At the end, all Wichita needed was a red jacket to match her Zoey ponytail.
Tallahassee's "farewell" to Columbus is "That'll do, pig", from Babe. Columbus even calls him out on it.
Also, Tallahassee makes a few references to Deliverance during the supermarket scene, the banjo being one aaaand...
"You got a purty mouth!"
A subtle one from World War Z. In the book, a guy in the Long Island mansion brags about his exact copy of Tony Montana's AK-47 from Scarface, despite the fact that Montana used an M-16. Cue Zombieland's opening, with a guy dressed as Tony wielding a Kalashnikov.
Tallahassee's ride on a roller coaster swarming with zombies brings to mind rail shooters like House of the Dead, especially Carn Evil, which, as it suggests, has you on a roller coaster fighting zombies.
The opening scenes are chock full of shout outs to other zombie movies:
The shout out to the Dawn of the Dead (2004) remake with the woman who has little girl zombies in her neighborhood. Also the opening moments in front of the White House is another shout out to the same movie.