Dwarf - Essentially a free +2 Con, since Cha is a dump stat. And all those little bonuses can add up. But the speed penalty can be annoying, especially since you can't wear heavy armor to cover it.
For a warblade, elves have the added bonus of being the only race able to qualify for the amazing Eternal Blade PrC.
Grey Elf - Strength and Con penalties. Next.
High Elf - These are a little better than grey elves, but not by much. Dex is good, but it hardly compensates for lost Con.
Wild Elf - A strong pick. Losing Int stings, but it's hardly as tough as a Con penalty. If you're restricted to Core races and want to play an elf (especially on lower point buys), I advise playing a wild elf.
Wood Elf - These are also a strong choice; I'd recommend them only on higher point buys, though, as you'll need to purchase mid to high scores across the board in order to end up with decent Con and Int.
Gnome - Gnomes don't make very good warblades, losing Str and using small weapons. But the smaller damage die can be compensated for without much trouble at all, and losing two points of Str won't cripple you too much - and on the other hand, you'll gain bonuses from your small size.
If you really want to be a gnome, go ahead; otherwise, though, you can do better.
Half-Elf - Ew. They're basically humans, but much worse. The only use here is qualifying for Eternal Blade without any penalties - but even so, snow elf is usually your best bet.
Halfling - At first these might seem like an awful choice, but, as ShneekeyTheLost notes,
A point of note about halfling warblades...
It's not as bad as you might think. The Str penalty equates to a -1 damage. The size modifier does about the same thing. In the long run, it doesn't hurt as much as you might think it does.
If you go with Halfling, you'll need to build specifically for this task. There's a couple of ways to do this:
1) Dip swordsage or blow a couple of feats to get a Shadow Hand stance. Then take the feat Shadow Blade, and make sure you can make it appear as though it was a shadow hand weapon (spiked chains, by the way, are shadow hand weapons). Replaces Str with Dex for damage. Weapon Finesse to use Dex to attack. Str is now a dump stat, but rather feat intensive.
2) Bloodstorm Blade/Master Thrower. Seriously, two points of damage isn't going to be hurting you here, and you can do an awful lot of havoc to someone who is bigger than you, so being small is an asset rather than a disadvantage.
Also, as a halfling, you can pick up Confound the Big Folk for more obnoxiousness.
Half-Orc - These are a nice pick. The damage to mentals isn't good, but it's better than penalties to physicals - and the Str boost is delicious.
Human - When Wizards wrote 3.5, they obviously had an inflated racial ego, because humans are awesome for basically anything. For a warblade, they're no exception. Feats are horribly scarce, especially if you're not allowed flaws, and the extra skill point is great.
There are a bewildering number of races to choose from, and so from here on out the only ones mentioned will be those black
and higher. If a race isn’t here, assume it’s not worth taking (though you are, of course, welcome to take it up with me).
These races are only those without level adjustment and/or racial HD – those with can be found below.
Aventi (Stormwrack) – Wonderful in an aquatic-themed campaign, though not as useful otherwise.
Changeling (Races of Eberron) – Changelings make awesome spies – and while you are perhaps not the best spy, their shapeshifting is still a very cool toy.
Darfellan (Stormwrack) – A prime pick in an aquatic campaign where you're forced to play a water-breathing race, and nice all-around. But make no mistake: you will get made fun of for looking like a whale.
Mongrelfolk (Races of Destiny) – While -4 Cha shouldn't be too big a problem, and the Dex-for-Con trade is good, the stats are lacking when compared things like orcs and neanderthals. Nonetheless, you could do much worse.
Neanderthal (Frostburn) – Not fantastic, as it has a penalty to both of your secondary stats. But still, that’s far outweighed by the bonus to both primaries.
Orc (MM) – A penalty to all your mental stats, but a +4 Str boost is really enormous. Definitely a fine pick, and better than those puny half-orcs.
Raptoran (Races of the Wild) – A great pick; the wings are more a boon than any measly +2 to Str or Con.
Shifter (Races of Eberron) – Longtooth or Longstride shifters are the obvious choices, and they make quite good warblades. They trade Int for Dex, but that’s a pretty fair exchange, and the goodies from shifting more than make up for it.
Skarn (Magic of Incarnum) - Bonus to Str, penalty to Dex. Come with built in natural weapons so you can still initiate maneuvers while unarmed without having to take Improved Unarmed Strike.
Warforged (Races of Eberron) – You’re a robot with a bonus to Con and more immunities than you can count. At first level you can potentially have armor better than plate, and with feat investments you can gain potent bonuses to it.
+1 Level Adjustment
The only variants here are those that are better than the standard race.
Badlands Dwarf (Sandstorm) – Again, if you’re in a desert campaign it’s worth looking at, but not otherwise.
Deep Dwarf (MM) – Slightly better than the standard, but not by much.
Earth Dwarf (SRD/Unearthed Arcana) – Str for Dex is a very nice trade – and the extra bonuses certainly don’t hurt. Superior over the hill dwarf.
Painted Elf (Sandstorm) – Dex and Int are really on equal footing for you, making this a pretty even trade.
Snow Elf (Frostburn) – The best elf, with the Con penalty traded for one to Cha (your one true dump stat).
Chaos Gnome (Races of Stone) - +1 LA.
Bonuses to Dex, Con, and Cha, though at the cost of Str. You trade the normal gnome benefits for a couple of SLAs; you are also, notably, immune to compulsion effects. You also - and this is the main draw - gain a reroll once per day, for anything. Rerolls are precious, and the immunity to compulsion is invaluable: with LA buyoff, these are potentially even cyan.
Whisper Gnome (Races of Stone) - A great race for small, more dextrous warblades; strictly superior to their standard counterparts. You gain a bonus to Con in exchange for a hit to Cha, plus a +8 bonus (half size, half racial) to Hide, a +4 racial bonus to Move Silently, a +2 racial bonus to Spot and Listen, and Silence as an SLA.
Strongheart Halfling (Forgotten Realms) – Without a doubt the best halfling, thanks to the free feat; however, you may be better just going human.
Aquatic, Arctic, and Desert Half-Elf (SRD/Unearthed Arcana) _ These are better picks than the standard half-elf, especially in a campaign geared towards their respective terrains.
Aquatic Half-Orc (SRD/Unearthed Arcana) – It’s…a half-orc, but better. Remind me why you wouldn’t pick this over its standard counterpart?
Jungle Half-Orc (SRD/Unearthed Arcana) – If you want to make a dragoon build, the Jump bonus can help.
Scablands Half-Orc (Sandstorm) – In a desert campaign (*cough*Dark Sun*cough*), the heat and thirst endurance can be a lifesaver. Otherwise, skip it.
Aquatic Orc (SRD/Unearthed Arcana) – In an aquatic or naval campaign, likely a better choice than standard orc.
Desert Orc (SRD/Unearthed Arcana) – Endurance as a bonus feat is excellent, allowing you to qualify for Steadfast Determination immediately. Very nice.
Water Orc (SRD/Unearthed Arcana) – Woah. Like a normal (already superb) orc, but they slipped an extra +2 Con in there, in addition to your already delicious bonuses. This is without a doubt the best kind of orc, and a truly fantastic warblade.
+2 Level Adjustment
Half Giant (SRD/Expanded Psionics Handbook) - Bonuses to Str and Con, but a penalty to Dex - so it might be a good idea to start with at least a 12 in the last. They have the always saucy powerful build (great for those tripper/knockbacker warblades), as well as LLV. There's also a mildly useful Psi-like ability for crowd control, but expect this to drop off in effectiveness dramatically at higher levels. Naturally psionic even makes these guys a possible choice for a psionic dip or for a warblade//psion in gestalt.
Goliath (Races of Stone) - Huge bonus to Str, a bonus to Con, and Powerful Build. Like a half-giant, but potentially even better - especially with the added benefit of bonuses in mountainous terrain.
Sharakim (Races of Destiny) - Bonus to Str and Int, with penalties to Dex and Cha. This is synergistic with the warblade's important stats, and you get some other minor benefits: darkvision, shadow affinity and orc racial enemy. Get cool shades to negate the light sensitivity.
Thri-Kreen (MM2) - With multiple limbs suitable for Multiweapon Fighting, tasty bonuses to Strength and Dex, and an absurdly high bonus to Jump checks, thri-kreen are a Tiger Claw adept's dream (and worth considering even if Tiger Claw isn't your focus). An older version granted them limited psionic abilities in exchange for an extra point of LA; for a warblade, the current version is much superior.
Higher Level Adjustment
Half-Ogre (Races of Destiny) - An enormous bonus to Str and Con, but penalties to Dex/Int/Cha. Large size, some natural armor, darkvision and the Giant sub-type. These guys will hit hard, fast and bring people down. Combining them guys with knockdown/knockback sounds utterly terrifying. If you can afford the LA, start at a high enough level to buy some or all of it off, or if it only eats one side of a gestalt, these guys can even become great.
Flind Gnoll - +2 LA, +2 RHD.
You'll score some considerable bonuses to your physical abilities - +6 Strength, +2 Dex, and +4 Con - (as well as a small natural armor bonus) which are the flind gnoll's main appeal. Only consider playing this race if you can buy off the LA; even so, the combination of LA and Racial Hit Dice will dog (pun not intended) you throughout your career.
Dark (ToM) - LA +1.
A nifty little template, it gets you Hide in Plain Sight and 10' extra movement, as well as a very large bonus to Hide. While perhaps better suited to the swordsage, and less appealing if you're not into hiding, this can make an excellent template for a small, deft warblade. Combines particularly well with races like whisper gnomes or strongheart halflings.
Draconic (Draconomicon) - LA+1.
This is good stuff. We land bonuses to Str, Con, and Cha, natural attacks to use with maneuvers as well as some minor skill/save bonuses, Darkvision, and LLV. Compares well with other LA +1 races but is a template! As a result, you can find some excellent synergies combining this with efficient LA +0 races. Draconic warforged? Draconic orc? Draconic water orc?
Dragonborn (RotD) - +0 LA.
Mechanically, this template takes your original racial abilities then tacks on +2 Con -2 Dex. You gain access to a draconic aspect, the dragonblood subtype and a few other minor benefits, while losing most of your other racial traits.. Can be combined with wood elf to net a +2 Str, -Int. Makes water orcs fairly insane.
Draconic Aspect can be a powerful ability as well. Mind Aspect culminates in Blindsense (an excellent perception boost), Wings Aspect gives solid flight (effectively replaces a flying magic item at high level). Breath Aspect could be fun, but doesn't scale (haha!) very well.
Feral (Savage Species) - +1 LA.
An excellent template. While you suffer a significant -4 to Int and -2 to Dex, and your hit dice become d10s, you gain +4 to Str, +2 to Wis, Darkvision, +10' to your movement speed, claw attacks (with Improved Grab and eventually Rake and Rend), a +6 natural armor bonus...but most significantly, at 4 HD - and this is why it's turquoise - Pounce. If you're using the LA buyoff rules, this template becomes simply superb, as it means you can gain Pounce without needing to spend a level in Spirit Lion Totem barbarian - and thus, while retaining a full 20 levels for whatever progression you wish. Do note, however: Savage Species was released under 3.0, so its use in 3.5 is subject to DM approval.
Shadow (LoM) - +2 LA.
Right off you gain +50% to your movement speed, some scaling Cold resistance, Darkvision, LLV, and a neat ability called Shadow Blend. Every four HD you also gain a special ability of your choice, ranging from a large bonus to Move Silently to DR5+1/HD to the ability to Plane Shift once per day to the Plane of Shadow.
Like Dark, potentially better for a swordsage, but useful for stealthy, dextrous warblades. Even you're not interested in stealth, there are some potentially very useful benefits to be gained.