We call it a dum-dum.
My step-sister calls it a "binky" (she's American) or "pacifier".
My friend's little girl used to call it a "Marmo" so the whole family ended up referring to it as a "Marmo". She is 2 now and says "dummy".
My Mum sometimes calls it a "Pipe".

Melinda - I had to laugh. We say "Hok up a gorby" instead of "Hack up a golly". Isn't it funny how one thing can be said so many ways