Infinite Wish Loop
"I will grant you three wishes, but no wishing for more wishes."
"Gosh, I wish I could wish for more wishes."
"... fuck."
Role-playing games with powerful wizards usually have a spell called "Wish" or similar at the top tier of spellcasting, and it's supposed to be the wildcard of do-as-thou-wilt magical effect. But any DM knows the problem with giving players a blank check: they're going to actually try to cash it in. If the game wasn't written by a noob, the spell description for the Wish spell will have specific limits on what can be wished for, including "No wishing for more wishes!" and "No wishing for more beings who grant you wishes" in order to prevent cheesing via infinite wish loops.
...Ha ha, screw that. The Wish spell is supposed to be an "I win" button, and we're going to win the fuck out of this game. This page should be a list of how to get nigh-limitless uses of the Wish-type spell effect in games.
Candle of Invocation Loop
This is for D&D 3e. Get a Candle of Invocation (8,400gp, could show up in the treasure for encounter level 12). If the Candle matches your alignment, you can use its gate feature. The Candle has caster level (CL) 17, so you can use the Candle to gate in 34 hitdice of creatures, and have them serve you immediately for 17 rounds without needing payment. This will destroy the candle, but no worries.
Gate in an efreet (10 hitdice). Among its spell-like abilities is "1/day grant up to three wishes (to non-genies only)". Wish one: Ale. Wish two: Whores. Wish three: another Candle of Invocation, pretty please. Cheese aficionados should recognize this method as a crucial step of the early versions of the Path to Pun-Pun. Newer versions bypass this by exploiting that Pazuzu grants Paladins one free, uncorrupted wish to tempt them.
Wand Surge
This one's for D&D's Eberron setting. Your character should have the 'Wand Surge' feat, and you've hopefully acquired a Wand of Unfettered Heroism with at least one charge left (or can just cast it yourself, but that takes too long). If you have, then get yourself a Staff of Wishes with at least one charge left.
Zap yourself with the wand, which gives you a free action point every round for one minute. Use that action point every round with the Wand Surge feat to use a magic item without expending a charge. One minute = 10 rounds, so that's ten uses of the Staff of Wishes without expending the last charge.