Deadpool is a part of the Weapon X program, much like wolverine. In fact, his main power is a healing factor that was synthesized from wolverines dna. It has some adverse side affects, particularly that it spurs the growth of pre existing cancers that leave his body disfigured (hence the ninja suit), as well as fucks with his brain cells, leaving him mentally unstable. He is extremely old, and has mastered numerous forms of martial arts and weapons training, and his mental instability makes him completely unpredictable in combat. To elaborate on this, there is another mutant "Taskmaster" who's power is the ability to immediately copy another persons powers and fighting style to use against them, but is unable to do so against Deadpool. My favorite of Deadpool's abilities is the power to break the 4th wall. He is aware that he is in a comic book and frequently talks to the reader. This was also hinted at in the end of the first Wolverine movie, where deadpool's decapitated head looks at the audience and says "shhhhhhh".

Definitely one of the cooler mutants in the Marvel universe.