Stuff like Shahrazad having you play a side game, Karn making you restart, Aeon engine reversing the turn order, Chaos Orb, goblin game, etc.

I've got a really half-baked idea to just throw all of these wacky cards into a deck to see what happens. Not expecting it to be good, just a fun thing to throw into the mix once in a while for casual play.

Sticking to "real" cards, no need to dip into the un-sets, they've made plenty of strange cards over the years.