{aphetto alchemist} + {mesmeric orb}
I got the combo from here
http://www.mtgsalvation.com/forums/the-game/legacy-type-1-5/developing-legacy/180860-tapped-out-infinite-tap-combo
so {Aphetto Alchemist} taps for its ability and target itself to untap? im not sure what im saying, hahaha
This would be fun with {Laboratory maniac} + {Phenax God of Deception} and {Horseshoe crab} mill yourself to the max
Or even just two of the alchemists. XD