I'm reposting the CTIV-3 ideas from earlier, plus adding a couple others:
The Tech Slaves: As a group we decide on one tech we really want (doesn't matter which one) and we click on that one, and then shift-click on Future Tech, and we have to follow the path laid out for us. (Someone else mentioned this idea in another thread, I apologize for not remembering who) All victory conditions will be enabled, however, if we don't actually research the Future Tech it's a "loss" (in other words, Renaissance Era conquest is a no-no)
Miller Lite: Our workers can only build the mill improvements: Lumber, Wind, and Water. The only exception: we can build a farm/pasture/mine/plantation/etc to get a resource--but only if a city can't work the tile (i.e. outside its working radius but within cultural borders). Everything else is the same. I'm thinking a Cultural Civ for this game (since our city placement will be 'awkward' for lack of a better word).
New ideas:
Anarchy International: REVOLUTION at the start of every player's turn (in Turn 1, not Turn 0). If there is something else to switch to, you must switch--in every category. No other variant rules. Will NOT be a Spiritual Civ.
Death from Above: Can not declare war on another Civ until Flight is researched. Before Flight, any wars must be fought defensively. After Flight, must declare war on every other civilization and remain in war until end of game. No land units/cities outside of our borders can be attacked by land troops unless hit by airpower first. Conquest will be only victory condition enabled.