I know it probably depends a lot on what style of music you mostly play, but is there a certain tuning you use more than others? I use the standard E tuning and drop-D a lot, but lately, I've been getting interested in open-D tuning, which is D A D A D d. You can get a lot of really cool tones out of that one :-)
not much the standard E, and then some open G. The open G is what Zeppelin and Rolling Stones and a lot of blues based music is played in. I like the tone a lot but primarily I just stick with the standard E. I've used drop-D almost exclusively when playing velvet underground stuff
mostly standard E tuning, half step down (Rise Against songs), full step down (Bruce Springsteen and The Gaslight Anthem songs) and drop D tuning (anything punk and metal).
I like to tune my one of my electric guitars and acoustic a full step down and stick a capo on the first fret for half step stuff and second fret for standard tuning so I don't always have to retune to play a song in a different tuning.