A common 1/1 haste for 1 mana that's not completely useless later on in the game. It does obsolete Raging Goblin, but I can't see much way round that unless I give this "~ can't block".

ROFL. I like the way you can use the haste to tap immediately if you want to :)

Note Skitter of Lizards already obsoletes raging goblin, so there's precedent. I think the combination is fine.

It may be too convenient that this is a one-drop useful later, but that's obviously one for playtesting.

"~ can't block" is, as MaRo and KEN point out today, a Black restriction. The red equivalent is "Attacks each turn if able"

Mmm, true, though it's a guideline they've broken several times. A creature with "attacks each turn if able" along with a tap ability just feels a bit silly...

But thanks to Jack pointing out Skitter of Lizards gives precedent, I'm inclined to leave this as it is.

"Attack each turn if able" would actually be very funny, because it would feel so over-eager, and yet, you can always tap it beforehand (and would often want to do so). But I'm not sure if it's funny only from a design perspective or also from a play perspective :)

If nothing else, it's a crazy version of Sootstoke Kindler.

Food for thought, though, I've always thought Renegade Doppelganger was pretty much equivalent to "T: Target creature you control gains haste until end of turn".