Showed up at a dive site on Maui without my fins. So we did the dive with Peter towing me.
Showed up at our local underwater park without my dry suit boots, so I stuck my Crocs on over my socks and dove with them (and spent the whole dive putting my fins back on).
Saturday, I went to do a reconnoiter dive at a site in Lake Washington, and realized after I got in the water that I had taken off too much weight for the aluminum tank I was using. So I picked up the biggest rock I could find and carried it through the whole dive (20 minutes, max depth 40 feet). Peter had TWO rocks
Went all the way out to Davidson Rock one day, and realized when we got there that the battery on the boat had died. We did the dive, and when it was time to go home, we had the guy in the other boat disconnect his battery, hand it over to us, we got our boat started, and gave him back his battery. Thank goodness the motor didn't stall on the way home!
Got to our local mudhole one day and discovered my computer battery was dead. No one had a spare, so I did the dive anyway, using my buddy's Liquivision (and it was pretty funny, because I know that particular dive so well that I'd ask myself before I looked at his gauge, "How long have we been down, and what depth are we at?" And I was never more than two or three minutes, or five feet off.)
Forgot my gloves once, and borrowed a set of extra large 3 mil gloves (this is in Puget Sound, mind you) from somebody at the site. Found out that, if you pull the Velcro on the wrists REALLY tight, the gloves don't have to be thick to be warm!
My buddy showed up one day without his wing. He did the dive anyway, using his drysuit for buoyancy.
I read this and think, "Wow, what a lot of rules we've broken!"