As a test subject in the same Weapon X program that had previously given Wolverine his adamantium claws and skeleton, Wade Wilson received a healing factor that prevented his cancer from killing him.Marvel Source
Wade soon escaped the program and became a freelance mercenary using the name Deadpool, working for various criminal organizations. At times he has teamed up with heroes as well, but these attempts at "being a good guy" rarely stick for long.
Wade is mentally unstable, though whether this is a normal state or is caused by his constant state of hyper-regeneration is unknown. One side effect of his mental state is the belief that he is not a real person but actually a character in a comic book.
My Deadpool is only level 32, but these are what have been working for me as well as a friend of mine with a 52 Deadpool.
-Skills-
Shoot All The Bullets - Should be your primary source of damage output. This skill ends most enemies in seconds and attacks as an AoE. I like to round enemies up and teleport to a place where only a few can attack you at a time then mow them down while they are lined up.
Armor Buster - For use on single targets or whenever you don't want to use your spirit. Since SATB doesn't really use all your spirit, you can probably substitute this for another skill of your choosing if you find yourself not using it very much. It's still good to pair this with an item that gains spirit on hit with a basic attack.
More Bullets - This is probably where some people won't agree with me. This is perfect in PvP if you find yourself low on spirit and health and unable to teleport. This skill gives you enough to teleport a few times, possibly more when both skills are maxed.
Bang Bang - Synergy for SATB. Not used on my bars, just there to complement SATB.
Bodyslide By One - Teleport. Extremely useful all around the board. The higher it is, the less spirit it takes to teleport. If you have enough spirit and find yourself unable to deplete it from teleporting, you can probably substitute some of the points to something else.
Power Ups - Used to heal or increase damage. This skill is extremely useful for healing. Teleport away and heal up then get back in the fight.
God Mode - No brainer. This skill is perfect all the time. Activates on its own and more points in it makes it last longer. If you're PvPing, at max level you can stay in God Mode for ~20 seconds with 0 spirit cost and 0 health depletion.
For solo, you can substitute some points for Lil' Deadpool to keep bosses occupied. This skill really doesn't need more than 1 point. Another skill others like to use is Foot Gougers, but with this build I really don't see the point. You can kite mobs through it if you want, but not being able to throw it any place but under your feet makes it less desirable. It's also quite useless against bosses when skills like SATB do much more damage and can be spammed over long periods of time.
If you have any input, please feel free to let me know what you think. I will try to come back to this and update it accordingly.