One level dips

[Yorrin]

Hmm...
How many full BAB classes are there?

You could build a melee combatant that can do a LOT with just one level dips. Toss in one class that gives casting and several that add +1 caster and you should be able to pull off a really good gish build!

Just off the top of my head:
Fighter
Barbarian
Paladin
Ranger
Knight
Duskblade
Warblade
Crusader
Hexblade
Samurai
Swashbuckler

So that's 11 base classes to start with (Barbarian and Paladin have alignment conflict, as do Hexblade and Paladin. Solve by using CE variant from UA.)

Note that 2lvl dips are often (though not always) more effective.
e.g. Barbarian 2 (for pounce and imp. trip)/Fighter 2 (2 feats)/Paladin 2(Cha to Saves)