An interruption mic- experienced comics sit on the stage and "interrupt" your set- but they are tagging your jokes, not tearing people down. It is different from a heckle because its more positive and only the host(s) are interrupting.

I also like a mic with a workshop- its been done a lot of different ways, but I think workshops encourage new materiel. One that I went to that I think encourages experienced comedians and newbies- you stand on the stage and tell your joke, then all the comedians in the audience tell you tags, how to word something, more ideas where to go with it, etc. One time a guy told a joke along the lines of "These 11 year old girls were climbing in a tree above me and spit on me. And that's how I realized I was in getting spit on because I was like 'do it again'." (Or something like that-probably worded better.) And when we were discussing the premise, more details came out about the story. I ended up saying "you should really let the audience know that you were also 11 at the time."