In case you'd like to read some of these but aren't willing to cut too deep into your Doritos Gorditas budget, check out Marvel Unlimited. It's basically Netflix for digital comics, and every Deadpool comic listed here is available to read on that service, all for like ten bucks a month. I'm not being paid to say that, but I really should be.
7. Deadpool fights zombie presidents
Everyone is kind of over zombies unless it involves a grizzled ex-cop, his annoying son and a badass lady with katanas, but zombie Presidents? That's a rancid artery of untapped potential. This would explain why the festering founding fathers play such a prominent role in the first story of the revamped Deadpool series, helmed by writer/Ohhh Heyy Didn't He Play the Mailroom Guy on Just Shoot Me Brian Posehn and the non-David Spade-adjacent Gerry Duggan. And you can trust that the artist knows his way around zombies, since Tony Moore is the guy who drew the very first Walking Dead comics.
The aptly-named "Dead Presidents" story arc sees the Merc with a Mouth battling the ressurected corpses of Abraham Lincoln, George Washington and like three dozen other old white guys with streets named after them. Brought back to this mortal coil by a necromancer, the zed presidents are nothing like their former selves. Well, except for Teddy Roosevelt, who was known to patrol zoos looking for fistfights.
Though you'd think this would be a job for the big-league superheroes, having Captain America duke it out with a dessicated FDR wouldn't exactly do the Avengers brand any favors. This is a dirty job, which is why SHIELD calls in someone a tad more unscrupulous. If the public were to see a dick like Deadpool headshotting Teddy Roosevelt, most would say "Yeah, sounds about right."
The whole thing is sort of light on plot, though you don't really need a reason to send Deadpool to space to fight an evil Ronald Reagan. The later stories in the Posehn/Duggan run actually get better, but any story with a humungous undead President Taft is a pretty good place to start.
Ah, the ol' naked zombie president with double-moobs. I wonder how Stan Lee feels knowing that, deep down, he's ultimately responsible for all of this.
6. Deadpool Kills the Marvel Universe
Most of Deadpool's comics are lighthearted and zany, with only the briefest of touches upon the twisted underside of the character. Deadpool Kills the Marvel Universe sounds like it might be another one of those stories, but writer Cullen Bunn and artist Dalibor Talajic crafted a world much darker than you'd expect. In the opening pages, Deadpool's "true inner voice" is awakened, and it tells him what he's wanted to do all along: Kill everyone.
When Deadpool blows Spider-Man's brains out, there's no joy to be had. No snarky quip, no delightful misunderstandings. You can see in his eyes; Deadpool is on a mission to murder everyone, and while that sounds like a hilarious idea, in practice it's pretty disturbing.
Naturally, there are some practical limitations to Deadpool's plans, like how he can't confront the Hulk without this happening:
The comic explains this by upping the capacity of Deadpool's regeneration abilities; it only takes a few hours for him to heal up after being completely dismantled. That, and the awakening of his psychotic subconscious seems to have unlocked his true potential as a tactician. Here, Deadpool uses Ant-Man's Pym Particles to make Thor's hammer so huge that it crushes its owner.
The entire comic seems to dare you to be entertained by the wholesale slaughter of do-gooders. You're not exactly supposed to be rooting for a ruthless murderer, but it's kind of hard not to forgive anyone who boops a god to death.