The idea that anyone would never bother to get a secondary profession - even if they don't use it - is simply laughable. At the very very least, it can unlock stuff for your PvP characters and give you versatility.
I personally like Ranger/ Mesmer. I heard Ranger/ Necro is good too. But that's the only combo I haven't tried so I have no authority there.
I always favored R/Ele because the Conjure skills were very strong. With new changes that make it so you can't use a Zealous grip have made me change my mind. I am now looking more at R/Nec using the curses line and R/Mo using the smiting line.