Glassdust Hulk - 3WU
Artifact Creature - Golem
Whenever another artifact enters the battlefield under your control, Glassdust Hulk gets +1/+1 until end of turn and is unblockable this turn.
This card is quite amazing at common. It's very useful mid-game, it's out of bolt range, it can become unblockable, and if you ever need to, you can always pitch it to draw a card.
It's just a great card. There's not a lot to talk about it since there aren't very many bizarre mechanics just a few little ones. Optimally he is a 4/5 unblockable for 5 mana cost, that can be a cantrip if it's imperative to get a removal card or counterspell.
He was probably pretty crazy in draft, assuming you could get your colors right, and with so many good artifact cards since Scars of Mirrodin (not to imply that there weren't any before), I could see this seeing play. Especially with some of the new cards like Glint Hawk.
Just a good card. If I played a U/W deck that wasn't CAWBlade, I might find room for at least one of these. 4/5