I usually tune with harmonics, especially since I play bass most of the time, and the only B string I deal with is a low B. When I do have to tune a guitar I usually tune the B by playing the 4th fret on the G string. I also usually check up on myself by playing some open-7th and "3rd string-3rd/4th fret" octaves. If I'm picking up a guitar that hasn't been played in a while, the octave checking is often a good way of seing what strings are in tune with eachother so you don't have to tune the whole thing.
Of course, if you're playing with other people this is all irrelivant.