Inspired by Nethack and other roguelikes, I've created a new 4E status effect:
You have been been turned into an @ sign!
While in this state:
-You never grant Combat Advantage
-All actions except free actions are considered Standard actions.
-You may not be the recipient of actions granted by allies through powers, class features, etc.
-Your move speed is 2
I imagine a dungeon where this is a permanent effect on one level: all the monsters are marked with a corresponding colored letter; all potions, magical items, and scrolls are unidentified until used; death is permanent...the possibilities are endless.