I love Aboleths, but haven't used one yet.
Since I was first exposed to D&D in 3e, it was the first monster I ever read about, and I still think it's one of the coolest aberrations ever made. I've been easily the most vocal proponent of an Aboleth miniature on the DDM boards, and I've planned out several awesome Aboleth encounters.
Currently, though, they're not in-theme for my campaigns, and they're too cool to just throw in somewhere, so I'm waiting to use them. Hopefully, WotC will reveal the existence of one in their next Huge set just in time for me to use one.
(also, was there -ever- an Aboleth miniature made for anything ever? Reaper's never made one, and I don't think Ral Partha did.)