These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Alternate Character Interpretation: Arguably, the Big Four are all dealing with the zombie apocalypse and the resulting tragedy in their own way. Tallahassee is all about killing zombies in creative ways so he doesn't have to think about his son being horribly killed. Wichita screws over the guys repeatedly because she doesn't want to deal with all the death. Little Rock is adamant about getting to Pacific Playland so she doesn't have to deal with the fact that everyone she knows is dead, other than Wichita (and Wichita is just trying to make her happy so she has a goal to focus on). And Columbus? Well, Columbus is actually kind of normal. Maybe repressing.
Angst? What Angst?: Columbus really takes accidentally killing Bill Murray in his stride, and Tallahassee seems to get over the death of his idol fairly quickly. Then again, so does Murray. Might be related to surviving a zombie apocalypse.
Award Snub: For the 2010 MTV Movie Awards, Jesse Eisenberg is nominated for "Best Frightened Performance" — but Woody Harrelson was not nominated for "Most Badass Performance"! Instead, Angelina Jolie was nominated for Salt, a movie that hadn't even premiered yet!
Columbus mentions how he's glad that Facebook is no longer relevant in Zombieland. His actor Jesse Eisenberg went on to play Facebook founder Mark Zuckerberg in "The Social Network". Even better, Eisenberg wasn't familiar with Facebook at the time and needed the director to explain the joke to him.
For those who recognize the Left 4 Dead influence and have a black sense of humor, people named Bill don't exactly have good luck with zombies, do they?
One-Scene Wonder: Sister Cynthia Knickerbocker, a sweet old lady who drops a piano on a zombie for Zombie Kill of the Week. Six seconds of screentime, and one of the most memorable scenes of the movie.
Periphery Demographic: For a zombie horror-comedy (and so, marketed to a male audience) this movie has a very large female fanbase; good character development for the balanced core cast and the Adorkable male leads probably contributed.
Too Dumb to Live: The sisters' first con job plan on Columbus and Tallahassee seemed to hinge on both of them being unable to bring themselves to shoot Little Rock. If Tallahassee were just a bit less compassionate, he might not have hesitated and instead blown Little Rock's brains out before Wichita could stop him.