With my present mate, we only use "safeword" because we haven't done much... though I hope that will change after we go on holiday next week Someone who came to play with us was rather amused, he said it was "incredibly unoriginal" - we explained that it was impossible to forget or mistake, and I do want to keep things simple for my mate, ease him into BDSM as gently as I can.

We've never had the situation arise where I needed to call safeword while gagged though; he can usually tell what I'm feeling through the look in my eyes. Plus we negotiate thoroughly before starting. Though I quite like the idea of giving some sort of code, and I've heard of people giving a set number of long grunts as a safeword.

Just my £0.02, I don't claim to be an expert or anything for obvious reasons :P