Talking of smoke machines, doing sound at a jazz/dub/freeform type thing, me and another guy were very hands-on on the desk (dub echo, mixing etc) and i turned the smoke machine on.
10 minutes later i looked up to see the whole club completely obliterated in smoke, just silhouettes of the band, the lights and this great dub music coming out.
It was awesome!
We didn't have fire alarms so everyone just carried on, but me and the other guy on the desk were pissing ourselves laughing.