I'm worried that this card wont look right to new people looking at the set. It feels like it shouldn't punish you if you paid two mana. Maybe we should just change it "Etb tapped" and "~ can't block" instead and drop the reference to black mana.

Kinda odd for black to NOT get a 2/1 for , yeah.
REALLY odd that you can't spend to avoid the punishment.

Maybe we could reword it to be...

Hired Gun
Artifact Creature - Mercenary
If less than two mana was spent cast ~, you lose 2 life.

I'm not sure if that's a common though. :-/

I note that every 2-power creature for 1 mana so far has been at least uncommon. I have a feeling that a set where drafters can scoop up four or five 2-power 1-drops has problems. (It's fine for there to be multiple 3-power 2-drops at common, like Porcelain Legionnaire or Daring Skyjek. I think it's just the possibility of turn 1 this, turn 2 two more of this, that's problematic.)

Sets can have 1cc 2-power creatures at common. Some fairly recent examples include Vampire Lacerator, War Falcon, Phantasmal Bear, and Bloodcrazed Goblin. If there aren't more 2-power one drops at common in the set, then this is fine.

I like this as is. You either get a colorless 2/1 or a suicide black guy. I'd be wary of making this playable for without the life loss, as that would make the wording much clunkier for little real gain.

Let's not forget Diregraf Ghoul as well.

...Buh. I... have no idea how I forgot about Vampire Lacerator and Phantasmal Bear. Yeah, okay, that's fine.

Yeah, me too. It's funny how W & G have seem to have the best 2/1 for C, but R and B and U have the common ones. I guess the other colours get narrower ones that can be common, but W and G get the ones without a drawback at uncommon.

Heck, and get 1cc 2/1s with upside. At uncommon, that is.

­Diregraf Ghoul is an uncommon, FWIW.