Continuity mistake: When Deadpool falls into the dumpster he has no swords, he left them behind. When he climbs out, they are on his back. They disappear again as he walks down the stairs to his apartment.
Continuity mistake: When Vanessa takes off Wade's mask at the end of the movie, he has a picture of Hugh Jackman's face stapled to his. When Vanessa removes the picture, the staple on Wade's chin is affixed and horizontal. In the next shot, it's hanging down. The third time we see it, it's back to position 1.
Visible crew/equipment: After Colossus and Negasonic Teenage Warhead leave the manor to go find Deadpool, the scene cuts back to the bridge where several gunmen are shown exiting cars and begin approaching Deadpool. In one of the shots during this, a gunman is shown exiting the seat of a car, with the camera placed behind him. In the shot, the reflection of a camera, cameraman and boom mic are perfectly visible in the side wing mirror.
Continuity mistake: When Wade and Weasel decide on the name "Deadpool," Wade is wearing gloves, but in the close-up, his hand is bare (and un-scarred).
Continuity mistake: When the glass chamber holding Vanessa falls off the deck at the end it falls top first, but when the concrete block is lifted off, not only is it the right way up, but it is also at a right angle to the way it fell, with no glass broken.
Factual error: When Deadpool is starved of oxygen, then causes an explosion, it is implied that the excess of oxygen, coupled with a heat source (match), causes the chain reaction which blows up the oxygen tanks. However, for a chain reaction to occur, fuel is also needed. Combustion is an oxidation of fuel. The only fuel present which is hot enough is the match. The hoses/ pipes and the tanks would not be flammable.
Factual error: At the end, when Vanessa is thrown off the helicarrier, it's easily 200 foot down for her. Even if the tube is strong enough to survive that and all the debris falling on top of it, she's not strapped in, meaning she would smack every which way and probably break every bone in her body.