Or do you use them as cannon fodder for the main character to mow through? This is common for my books, because they are action oriented, so there has to be some minor thugs at least to get taken out. Now I don't spend much time developing them as they are usually introduced and killed, taken out in the same scene.
The one twist that I like to implement is to introduce a thug that you think is just going to be killed, but surprises you because he escapes, or does enough damage that the main character has to escape to survive. This usually works on a couple levels. One it keeps the reader guessing whether or not the normal thug will stay around, or die quickly. It also introduces minor subplots that drive the main character in directions that he wasn't expecting.
What are your favorite things to do with minor characters?
Do you use them and lose them, or do you like to build them up for a while only to be handled later?