I went as THE WEB - as in, a spider and a spiderweb.
I wore black pants, black turtleneck shirt, and on top of that white fishnet with holes cut in it so as to drape over head and arms - then I had a lot of rubber bugs - flies - grasshoppers - dragonflies etc. tangled up in the fishnet. On my head I wore a big hat that was a giant spider to complete the effect. That costume was a big hit, and when we had a contest I came in second!
A variation on that costume that I created for another party I called THE CATCH OF THE DAY.
In that costume I dressed in browns and olive green colors - draped a brown thicker fishnet over that, and I had tangled in that a set of fish lights - so I could actually plug in to an outlet and light up! I wore on my head an insulated green hat and on my hands I had oven mitts that were just the right look and color to double as fish fins, and I wore a fish nose ( held on with an elastic band ). That costume was a big hit as well - especially the lights - though I must admit that plugging into an outlet for the full effect somewhat limited my mobility at the party and later when we went out to the bars!