Uncommon cards can be recognized by a silver color of the edition, located at the middle right of a card. Uncommons have a variety of strange abilities, a mix of common abilities, and sometimes make powerful creatures even more powerful.
Creatures such as Vampire Nighthawk, which has a mix of powerful abilites, or Overrun, which gives each of your creatures +3/+3 and trample until end of turn, are very good uncommons. Other uncommons, such as Mold Adder, Fatestitcher, Gomazoa, Exuberant Firestoker, Hedron Crab, and many other good uncommons can do lots of damage to an opponent. Their abilities may not always be as good as rares, but they can do a lot of damage if your opponent can't do anything about it.