OK. I won't be the first to break the 5 app rule so I don't feel bad.
I'm leaving Beautiful Widgets out because I'll just assume EVERYONE has it
Games:
Stupid Zombies - hitting zombies with fewest bullets
Curvy - puzzle, line up.... lines
FlightControl - see who can sleep the longest. jk. land planes
Gangstar Miami Vindication - gta wannabe
Shadow Guardian - Uncharted/Tomb Raider wannabe
For fun:
Scanner radio - police/emergency scanner
Akinator - guesses the actor or fictional character your thinking of
A world of photo - send and receive photo's around the world (fun if you can ignore all the body parts)
c:geo - AWESOME geocaching app
Netflix - movies and shows
Useful:
Ringo pro - individual ringtones and alerts for each person
Cardiotrainer pro - keeps track of your runs and more
Airborne - makes your phone a mouse
Documents to go - a mini Microsoft office
Moon+ reader - fav book reader (like better than aldiko)
Honerable mentions:
Bump - send stuff to other people by bumping devices together
Waze - GPS directions and driving pac-man type game
Soundhound and shazam - music recognition (sounhound even rocognizes humming!)
Lyric legend - match lyrics to part of song it'd be played
My migraine log - unfortunately gets used often. Great for keeping track.