I rotate through about 4. Currently it's the intro to John Fogerty's Centerfield (in honor of baseball season). I also have custom ringtones assigned to about 10 individuals. My wife's is the DeBeers theme (the diamond people).
CTU Ringtone for most, one has the NFL on FOX. I also have the text sound used on House of cards but I customized it a bit and I use the chirp from The Unit.