Creature — Wolf 2/1, 1G (2)
Common
Creatures with power less than Wandering Wolf's power can't block it.
Humans still feared wolves, though no connection between them and the curse of lycanthropy had ever been proved.
Illus. Tomasz Jedruszek

5/1/2012: The comparison of power is only done when blockers are declared. Increasing the power of a blocking creature (or decreasing the power of Wandering Wolf) after this point won't cause any creature to stop blocking or become unblocked.
Legal in Vintage (Type 1)
Legal in Legacy (Type 1.5)
Legal in Extended (Type 1.X)
Legal in Standard (Type 2)
Legal in Classic (MTGO)
Legal in Commander
Legal in Modern