Reveillark + Saffi Eriksdotter + sacrifice outlet = infinite sacrifices, ETBs, and recursion of a creature with power 2 or less (Interesting ones listed here)
How it works:
- Sacrifice Saffi Eriksdotter to activate its ability targeting Reveillark
- Sacrifice Reveillark, putting both Reveillark's leaves the battlefield ability, targetting Saffi Eriksdotter and up to one other creature with power 2 or less in your graveyard, and Saffi Eriksdotter's delayed trigger onto the stack
- Resolve Reveillark's ability and Saffi Eriksdotter's delayed trigger, putting both onto the battlefield
- Repeat