Teacher of Heroes (Modern)

Basically an aggro-midrange deck that can handle longer games by drawing cards and leveling up early game creatures to stay relevant later on.
Venerated Teacher and Time of Heroes are the turbo-drive of the deck; you can win without them, but if you do get them out then your opponent will be hard-pressed to overcome your army.
Tezzeret's Gambit and Enclave Cryptologist form the main card-draw base, helping you get the all-important Venerated Teacher and Time of Heroes. Temple of Enlightenment can help get the card-drawers or the key cards themselves, and can be used with Azorius Chancery for repeated scrying.
Most the other levelers can be played cheaply and get at least one counter quickly, after which the proliferaters take over. With all you creatures leveling up potentially multiple times a turn, you can ignore the main weakness of level up (that you invest a lot of mana in one fragile creature).
Finally, Fuel for the Cause may seem out of place, since it costs 4 for a counter while everything else is about attacking, but sometimes you absolutely need the hard counter (Wrath of God was the main reason it was added), and it does of course proliferate.