Martyr's Soul
Oracle Text
Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for
or one mana of that creature's color.)When Martyr's Soul enters enters the battlefield, if you control no tapped lands, put two +1/+1 counters on it.
Green, though, has mana dorks and "untap all lands" effects, so you could see him in GW a lot.
No tapped lands. You have to Convoke the entire cost.
Here's a more realistic situation. Turn one Leonin Vanguard, turn two Saproling Migration unkicked, turn 3, tap Leonin Vanguard, both saproling tokens to cast this guy as 5/4.
Edit - NB that Goblin Instigator, Lazotep Reaver, and Raise the Alarm can be substituted for Saproling Migration, so there's a few ways this might become a frequent occurrence.