MTG Combo: Greater Good + Mikaeus, the Unhallowed + Walking Ballista

This does infinite damage, infinite card draw, infinite card discard and infinite sac triggers. Note that the discarding is larger than the card draw so you'll never end up with a hand with cards.

This combo is relatively simple, but easy to forget one crucial part: Mikaeus gives non-humans +1/+1 along with giving them undying. This means that creatures can never die from using their effects to remove all their +1/+1 counters, meaning you need a sac outlet to kill them.