Have you heard of the awesome spell
Surelife? It's practically begging to be used to break the game, with its vagueness and its potential for invulnerability. Here's what I thought up when I saw it:
Step 1: Get a second head. There's an item, from Dragon Magazine, I think, that gives you one, but it might be evil, so let's try something else. The multi-headed template from Races of the Wild gives you exactly that, but for a steep LA. We only need this to be temporary, so it would be much easier to use scrolls (if you're not a caster already) to transform into an Ettin, a Hydra, or (with Wild Shaping) a 2-headed snake, which is a perfectly normal animal mentioned in some other sourcebook.
Step 2: Find a cave with a precarious stalactite barely hanging on to the ceiling and stand right underneath it. Wait, it gets better.
Step 3: Cast Surelife on yourself, keeping you alive if you happen to (completely accidentally) get slashed by a 10-ton, naturally sharpened slab of rock. You know, just in case.
Step 4: Put on a Ring of Regeneration. See where I'm going with this?
Step 5: Oops. The stalactite just happens to fall and slices you in half. Not to worry, though. For 1 minute / 2 CL, each of your 2 halves are still alive. You regrow the rest of your body within 1 round, "even heads of multi-headed creatures," and suddenly there are 2 of you, each with exactly the same properties as you had before this process, and each one undeniably still "you."
Step 6: Repeat. Surelife lasts for minutes, and each stage of the cycle takes only 1 round, so feel free to look for other similar natural ways to get cleaved in two before the spell wears off. Do this enough times, and you should have a potent army.
The clones are all still "you" for all intents and purposes. Does that mean that you share spell slots, HP, turns, and familiars with them? Do you get less XP for being in a group, or the same amount because you're really alone? Can you use the Fusion power to become a super-character? I have absolutely no idea. But it's an interesting, low cost, low time, low requirement method to take over the world, so I'd say it's a TO mission accomplished.