As an audience member, I LOVe the gimmicks, as a player I find them quite humiliating, and hard...sometimes fun....
For example, a good gimmick:
We played the Stripper, the trombone soloist (female so it explains were she aquired the gimmicked product) had a lacy red bra attached to her slide, as 2 percussionists (a young dancer, and an older man good for a laff) pretended to put on a show.
An Interesting gimmick:
I once saw a band claim they paid big dollars and got Tara Fitzgerald in to do the Aranjuez flugel solo.....The nose gave it away as a former gladstone boy, and a good friend of mine....well the nose and a crooked embouchere, which we had trademarked!
A bad gimmick:
Swan Lake, performed by the tuba section. A plumber, an Electrician, a gardener, an engineer and a music teacher.