What's the most important piece of equipment you've accidentally forgotten to take to a gig? and how did you get around the problem?
In my case, the only thing I forgot to take once was a t bar for my lighting. I just put the lights on the floor, so I got away with it.
I know one guy who probably has an IQ lower than his shoe size...as he once forgot to take his SPEAKERS to a gig, doh!