What I Want to Run, In No Particular Order

• something sandbox-y
• a published module
• a megadungeon
• the party is a group of young, bored, reckless nobles who occupy themselves by causing trouble for their elders and their rivals
• kitchen sink post-apocalyptic: "wizards, dinosaurs, mutants & lasers"
• the new 4e default world
• Eberron
• something really dark ages
• fantasy Europe -- "Europa" or something of that nature
• pirates!
• old west
• ancient desert ruins
• steampunk
• interplanetary sailing ships with that baroque/victorian feel, "aether" and the spinning models of the solar system and everything
• everyone rides dinosaurs
• something like the setting in Jak 2, and the parts of 3 that weren't stupid
• Tamriel (Elder Scrolls setting)
• dragonriders for the Queen, who lives in an airship
• Expedition to the Moon!
• fast cars and the idiots who drive them
• magic fast cars and the idiots who drive them
• noble families based on hereditary wizardry
• 1st-20/30th: the players ascend to godhood and found an empire in the process
• that same world, 1000 years hence