If you want to keep it simple, the easiest way to break the game is to look for ways to overcome a class's natural weaknesses.
Sorcerer: Basically, you give up versatility for the ability to cast the same spells over and over. So I say, purposefully pick all the spells that allow you to do a zillion things. The shadow spells and Summon Monster are at the top of the list, but have you ever considered how many different ways you can abuse a high damage ranged touch attack? Scorching rays and orb spells can allow you to quickly and easily neutralize enemy casters, destroy weapons, open doors, etc. Telekinesis can disarm traps, hurl enemies into hazards or their own area effect spells, neutralize low-Will melee opponents, trip charging opponents, create decoys, and deploy alchemical items.
Cleric: Just pick any two domains that let you do stuff that has nothing to do with the run-of-the-mill clericly. Ex: Destruction allows the cleric to kill things a lot, Magic allows you to be a backup evoker or transportation specialist, Fire allows you to become a damage dealer, etc.
Fighter: Stuck at home with nothing to do? Take two levels of Rogue and sink every last skill point into Use Magic Device. Plus, you get evasion. Now you are a utility caster. Receive a diploma now for experience you have already earned.
Another approach is to purposefully break the usual numeric limits. The half-minotaur lolth-touched thing is one approach, but not the only one. As a full caster, you can identify individual spells that break the usual ranges. Telekinesis and Grasping Hand both use your caster level in place of your base attack bonus, and grappling and other manuevers generally ignore armor in the first place. Can you think of any ways to get your caster level higher than your character level? Yeah, me, too.
