You can get a 'Cool Light' that flashes different colours in time with music. (it's LED)
Also, if you're on a budget, look at an Alesis 3630 compressor; it's a pretty poor compressor, but it's cheap and has lots of cool lights on the front. Plug an unused output into it (tuner out, for example) to make the lights move, and just don't use the compressors output in your signal chain.
The worst I saw was a guitard in a touring band with a 24u rack with 4u of rack gear in the top, and
the rest of the entire rack was filled with those 1u level meters, all hooked up to different channels going at different times.
