Growing Rites of Itlimoc / Itlimoc, Cradle of the Sun Listed at: $7 Growing Rites of Itlimoc fetches you a creature when it ETBs and then transforms into Itlimoc, Cradle of the Sun once you control 4 or more creatures
Take my deck, for instance: When we were still forcing Sapling of ColfenorSapling of Colfenor as commander, this card was worth the four mana because I could see that I had a creature on top to draw, or could get a land off the top of my deck so I didn't whiff
Minas Morgol, Dark Fortress Minas Morgul was the twin city of Minas Tirith before it fell to the forces of Sauron
Add cards that help you produce more mana or the right colors of mana
We have a couple other powerful tricks up our sleeves, but Thumb is definitely the most important one
2 Leonardo, Sewer Samurai Creature Falling just short of the top spot is Leonardo, Sewer Samurai, mainly because its sneak cost is virtually the same as its base cost