Pretty much half the stuff already mentioned, mostly tools, spare o-rings for rental tanks and my own regs, lube when i am changing items out that have o-rings. I also have a spare light, mask and computer that occasionally sees use from others forgetting stuff or their's goes downhill and they dont have a spare - unlike Baitedstorm i have had to lend stuff to other SB'ers. I am thinking of expanding my dive bag/box and making it more substantial, throwing out useless stuff, between this thread and the other quoted on the first post i think i can make a better go of it! I have recently done the same with my first aid kit, now fairly competent for most of my adventures i believe.
