With my blue tri beagle, the guesses tend to be pretty accurate, with people sometimes mistaking her for a basset.

With my lemon and white beagle, I get all kinds of fun stuff. I get the same line some other people have mentioned here "That breed doesn't come in that color!" Even though he has excellent conformation for a pet/field beagle, people refuse to believe that's what he is. They usually guess JRT. I have also heard corgi mix, 'puggle', Golden retriever or yellow lab mix (I guess those are the only yellow/gold colored dogs they can think of, because there's no other resemblance) and baby pit bull (from people who apparently have never seen real pit bull vs. small hound heads before).

With my fiancee's mystery mutt, the most common guesses are corgi (and she is colored just like one) and pom (she's got a somewhat pom-ish head, but the body is nowhere close) and chihuahua (I don't see any resemblance). Hard to laugh at those guesses too much, though, since all we can do is guess, too.