John Pearse on my 12-string, and I keep the used ones to use on my Harmony acoustic,
LaBella nylons on my Yamaha acoustic, DR stainless wound on my electric basses and D'Addario phosphor bronze my acoustic/elec bass. Mostly cuz that's whats easily available locally, but tried a couple different brands on the Yamaha and nothing seems to sound as nice as the LaBellas (mediumweight i think), plus once they're broke in, stay in tune and last forever. I put DR stainless strings on my Ibanez 4string when the originals wore out, they feel lots different and sound a lot more tinny when playing unplugged but sound good thru the amp. My Ibanez 5string came with them already on, but I like the phosphor bronze on the Fender acoustic bass the best, kinda hard to describe "why" they just feel "right"...