UPDATED: Grenadier (3.5 Base Class) PEACH!

[Grod_The_Giant]

I'm not necessarily opposed to a 10-level base class as a concept, but it is... highly irregular. If you can't think of enough abilities for the latter levels, it may be better off as a PrC.

The Grenadier’s class skills are Appraise (INT), Concentration, Craft (Explosives) (INT), Decipher Script (INT), Disable Device (INT), Gather Information (CHA), Intimidate (CHA), Knowledge (Arcana) (INT), Knowledge (Explosives) (INT) Knowledge (Architecture & Engineering) (INT), Profession (WIS), Search (INT), Tumble (Dex), Use Magic Device (CHA).
Skill Points at 1st Level: (4+ Int modifier) × 4.
Skill Points at Each Additional Level: 4 + Int modifier.

A nice big list, alright. I'm not sure why some of the skills are there, though-- Decipher Script? Knowledge (Arcana)? UMD?

[I'll note here that your BAB progression is off; level 9 should still by +6/+1, leaving level 10 at +7/+2]

Class Features:Weapons and Armor Proficiency: A grenadier is proficient in simple, and martial weapons. Proficient in armors up to heavy.

You might want to copy the "official" wording here-- "A grenadier is proficient with all simple and martial weapons and with all armor (heavy, medium, and light), but not with shields."

Elbow Grease: The Grenadier gains a +2 bonus to all Craft checks. This bonus raises to +4 at 6th level, and +6 at 10th level.

Fine, although it might be more fun to make it scale with level-- adding 2/3 your Grenadier level works out about the same math-wise, but the bonus goes up more often.

Bombardier: A 2nd level Grenadier has a knack for throwing explosive. This feat gives you an exotic weapon proficiency that allows you to throw small sized explosives as a ranged touch attacks.

Is this a feat or a class ability? Either way, "small sized explosives" is a strange, unofficial category. If you mean things like alchemist's fire, it's already a ranged touch attack. The ability might be better off boosting the range increment.

Quick Draw: At 2nd level a Grenadier gains the Quick Draw feat.

Useful.

Trap Sense (Ex):
At 3rd level, a Grenadier gains an intuitive sense that alerts him to danger from traps, giving him a +1 bonus on Reflex saves made to avoid traps and a +1 dodge bonus to AC against attacks made by traps. These bonuses rise to +2 when the Grenadier reaches 6th level, to +3 when he reaches 9th level, to +4 when he reaches 12th level, to +5 at 15th, and to +6 at 18th level.
Trap sense bonuses gained from multiple classes stack.

OK. If you want him to be a trapmonkey, you should probably give him the Trapfinding ability at first level.

Twin Bomber (Ex): This feature gives a 4th level Grenadier, when throwing palm sized explosive, this ability, allows you to throw an additional palm sized explosive per attack roll.

What is a "palm sized explosive?" I mean, the description is clear, yes, but 3.5 D&D is a very rules-heavy game, and things generally need to be spelled out explicitly.

Volley of Bombs: This feature gives a 7th level Grenadier, when throwing palm sized explosives add 2x your dexterity modifier to your damage rolls.

See earlier point about explicitness; otherwise, a nice ability.

Weak Spot (Ex): A Grenadier can gain this ability only after reaching 8th level. When using a thrown weapon against a target of her size or larger, the character can make a ranged touch attack instead of a normal attack. If the attack hits, the master thrower does not apply his Strength bonus to the damage.

You already granted this ability in Bombardier.

Produce Flame (Sp): A 10th level Grenadier may cast produce Flame as a spell-like ability at will.

...aaaand, suddenly we get magic? I'm not sure why you give this. I guess the spell is sort of like throwing a bomb? I'd recommend against if, if for no other reason than that it's a pretty crappy spell at first level, much less tenth.

Good question. Most of the explosive can be found on the d&d wiki

http://www.dandwiki.com/wiki/MSRD:Ex...Splash_Weapons

The D&D Wiki is not an official source, and D20 Modern is not generally compatible with D&D. The rules, maybe, but the setting, not so much. If you want to use these rules, you should make that clear in the class. I recommend against it, though-- nothing breaks immersion like pulling out modern technology in a swords-and-sorcery world. Heck, C4 would be just as out-of-place in a Pirates of the Caribbean setting as in a dungeon crawl.

General Thoughts
I like the idea, but the execution is, sorry to say, a bit wobbly. I'm sure it makes sense to you, but D&D is a system that really needs things to be spelled out.
My recommendation for this class? Borrow a page from the Warlock. Craft bombs that deal 1/2-2/3 your class level damage, then throw them around. Learn new "Recipes" to make your bombs do different things-- produce smoke clouds, affect an area, deal fire damage, be remotely detonated, and so on. At later levels, you can get near-supernatural effects, like bombs that inflict negative levels and so on. It would add variety, and wouldn't require you to brew up a whole new set of rules for fantasy explosives.