Personally, I like Goblins. I just enjoy their mischievous nature and innate curiosity that leads them to play around with any new toys they get, even if it is out of their understanding or control and in the end leads to them losing a few mates. I always found this mindset hilarious and perhaps I find it appealing because it contrasts with my grounded and cautious mindset. Not to mention as a rule, as a magic the gathering player, Goblins have the best flavor text.
EDIT: I am also fond of the Skaven from Warhammer, those are the ratmen to those who don't know about the lore. Hell, that's where I got my username from (started off as Clan Rat, changed it after I got kicked from countless games cause they thought I was recruiting). This is for some of the same reasons as goblins, but also because rats are one of my favorite animals (hardy and can survive in nearly all environments, not to mention despite what anybody else says, domesticated rats are damned cute) and I enjoy the concept of a vast civilization existing under the feet of everyday society.