Short over two points of bund vol on expiration day and there is a plane crash or earthquake somewhere in the world (I can't remember now, this was about two years ago...) and the market took off north and I am swinging 25 lots at the futures market trying to anti-scalp and am not getting any futures. I am swinging like a mad man all the way up and getting nothing so I keep swinging faster and for more size desperate to get an anti-scalp off since we have just rallied about 45 ticks in only a couple seconds. Little do I know that I have my software set so that when I swing at futures it routes a limit order. Everyone of my swings was going into the market as an order and staying in the market. We topped out about 50 ticks up and then spiked down a quick five ticks at which point I was filled on over 200 futures and then the market gapped down about twenty ticks in my face while I sat there stunned at what had just happened. About 45K in my face. Learned a valuable lesson that day though, if you are short vol and the market is going crazy, don't swing at futures, swing at options, but ouch.