Red: Summon: Esper Valigarmanda - Red 4s tend to be a dime a dozen in cubes with rares in them, but not a lot stand out from the crowd aside from Headliner Scarlett (since it usually just ends the game) and Pyrogoyf (which usually kills something, or someone.) I like that this does what the usual haste suspects do - deal some form of evasive damage, but this one lets you eventually cast something from the graveyard if it survives, which is a good bonus if this doesnt just die in combat
In a Commander deck with K'rrik, Son of Yawgmoth at the lead, you can turn the black mana in your spells into Phyrexian mana, letting you pay two life instead of paying the cost
The actual effect changes based on the card its on - so you might be able to just draw a card, or you might be able to put a dragon into play from your hand thats tapped and attacking
There are quite a few token-doubling effects in white now, with Elspeth, Storm Slayer and Ojer Taq, Deepest Foundation helping establish a board in no time, along with a few other spells