Well, put like that...
Sarevok (always)
Imoen (always, though this wasn't always the case)
Yoshimo (usually, though this wasn't always the case)
Valygar (very often - he rocks, and I like his personality)
Edwin (very often, even in an otherwise good party)
Anomen (often - I don't like his romance or personality, but his undead turning is spectacular)
Jaheira (sometimes)
Viconia (sometimes, though usually only if playing her romance, or the friendship mod)
Minsc (sometimes - used to be a staple, but I tired of him)
Keldorn (sometimes - I used to always take him unless playing evil, but now I feel guilty for taking him from his wife)
Aerie (hardly ever - I have tried her romance but I dislike her)
Jan Jansen (hardly ever - I used to take him all the time, instead of Imoen, but you can only listen to his stories so many times...and I prefer her now)
Haer'Dalis (hardly ever, though I tried him last playthrough and quite liked him)
Korgan (hardly ever. He's a good fighter but I just don't like him)
Mazzy (hardly ever. Taken her through
SoA once, but never
ToB)
Cernd (tried him once. He's OK. Won't rush to do so again unless he gets mod content)
Nalia (never. I should try her though)