Clan event ideas

This is another thread to see what everyone wants to play.

Commander has been added to our rotation so I would like to hear other ideas for clan games.

Personally, I like the idea of a BYOB (Build Your Own Block) but in order to keep it a little fair (and to promote more forum traffic) I think that we should have to post the blocks and core set we are using in another thread. Just an idea...

Rainbow Stairwell is an offering from DP. The rules can be found here:
http://www.starcitygames.com/magic/misc/6339_The_Compendium_of_Alternate_Formats_Entry_Four_Rainbow_Stairwell.html

There are many different formats out there so lets hear what everyone likes to play first and then we can all vote on it.