I'm partial to "Bullet Sponge" or "The Infected" but I have to say "The Living Impaired" is growing on me...
As for different types I call them Reavers, Stalkers, Wraiths, Shamblers, Crawlers and those are in order of danger from greatest to least.
Assuming freakish mutations are possible there are also the L4D nicknames and a few others I've made up but those aren't relevant to this discussion.