While no one is really complaining about something missing from Deadpool, there were numerous things that didn't make it into the final cut. Whether they were for budgetary reasons, reworking of the story, or just deemed too offensive, all of these things were omitted for some reason or another. Mr. Sunday Movies has done us all a favor and compiled these all into one place for our what-if needs.
Most of the deleted scenes were extensions of ones that made the theatrical release, like the highway fight with Ajax and his cronies, or the finale. Both of those scenes had additional sequences, but because of budget concerns they got hacked. Cameos and villain features also frequently got the ax. At one point characters like Taskmaster, Garrison Kane, Sluggo, and, of course, Wolverine were all rumored to make an appearance, and initially, they were. The previous three were all cut due to costs, and while that also factored into why they didn't use Wolverine, his was also related to issues of scheduling.
The two most glaring omissions were two scenes that were completely cut from the film. In the first one, Wade travels around the world to see if his cancer can be cured. When he comes upon someone who claims they can, yet turns out to be a con, Wade deals with it the only way he sees fit. By ripping out his heart.
The other scene was a montage of Wade attempting to kill himself over and over again, in a variety of ways. That might have led to some funny moments, but ultimately was deemed not needed. Also deemed not needed (and by the point of filming rather offensive) was a running gag featuring Amy Winehouse. The camera would cut to her almost dying throughout the film, only to be hit by a bus during the final credits. Deadpool would then say "and you would've thought it'd be an overdose". At the time, it was just a joke, but since she actually did die that way, they probably thought best to take it out.
There is plenty more left on the cutting room floor, so check out the full video to see them all.