Ok now if i was able to pick guest characters for either Mk9 or the new Mk game then it would be these three below.
PS3- Devil from tekken 2
Xbox360- Skorge from gears of war 2
Both consoles- Lanius Legate from Fallout New Vegas
im a fan of those three games, lanius may be from a diffrent style game but he is a brutal warrior and a savage, i always felt like he would be an interesting character in Mortal kombat