A pitch black, dark creature because I have always loved darkness, because I love when there's nothing to see and I can actually relax.
Hunched over, for I am lazy and don't care to carry my own weight sometimes (Keeping my head up is too much work

)
The oversized left arm, because I often find it to be the more useless of the appendages, so by overcompensating and turning it into a large, mauling hammer of a hand, or a blade arm in other cases, or the arm that I can shape into many horrible objects in other other cases. The left arm always gets the unique attribute, while the right contains my blade of preference. Usually a plain black katana with no guard(Though it's been a scythe lately. Straight stick/staff and towards the end, a blade with the sharp edge facing down, sticking about 3 meters out)(Also, both hands are clawed at the end, to clarify >< )
The spines across the back, because my own spine seems to jut out and make sitting in many chairs quite uncomfortable(I'm too skinny, so it sticks out about an inch from my body ><) Also the reason the creature is generally skinny. Same with the 2 main spines that stick out quite far and are near the top of the spine at either side. I want to say they're extensions of... a plate. I don't recall what that bone is, but it sticks out of your back when you move your arm across your chest.
With the face, It is only a large mouth(razor sharp teeth and all) that appears to be in a permanent smile. Featureless otherwise, for I never look how I feel I should. My hair doesn't look right, my face doesn't look right, so I like to set it aside. The only personality trait I feel does fit me is insanity, which I do tend to get into temporary fits of which make things quite fun(thus the demonic smile.)
Legs jointed in the way you'd think of a Minotaur's legs to be jointed. Not only are these the types of legs I keep coming back to again and again, but you can vaguely imitate the look by walking on your toes so that the heel of your foot is in the air. It's the way I walk when I sneak around, and it makes little sound.
And the tail, because for one, tails are awesome, and two, because something hunched over as this creature is would require support. Also, I imagine he would often be holding on to the end of the tail with his right hand, as I almost always seem to have my hand looped in something, whether it be my pocket or a string, it's always on something.