I've never been broke by tickle torture. My girlfriend usually gets me going and cuts out long before I'm at risk of breaking. A couple of good lines about how 'mean' she is, and she backs off.
I have a buddy that is an aerobics instructor. Once in awhile I'd meet him at the locker room at the gym when his class and my work-out ended at the same time. I stand 6' 205lbs. of muscle. I had 2 inches and 55 lbs. on the guy. Once, he took about 10-15 seconds worth of tickle-jabs at me. Man, this guy could have been a boxer -- damn fast. I'd react and try to block and he'd have landed two other shots. Told me I was all nerves and laughed at my situation as I kept backing into a locker. Not much I could do about it. Its not like I'll fight any guy that small, and definitely not a friend pulling a prank. I couldn't tickle him, each time I moved toward him he'd tickle a rib or armpit and I'd be trying to stop him again...
The worst I ever had, I was working on scaffold and holding up ceramic fixtures (about 70-80 lbs. overhead work). We were working in a old hall doing refit work. It was summer and hot. I was working on my own. I hadn't bothered to put my shirt back on after our lunch break. One guy on my crew was down the hall feeding wire. We had to hook up the bulbs in the old fixtures before locking them to their mounts. This left me with my arms up over my head holding the fixture in place till my buddy could come back, and finish wiring it up. Then I'd be able to lock it to its mount.
Another guy on our crew saw me alone holding up the fixture. He came into the room and jumps up the scaffold. This guy was had a medium build and was about three inches shorter, something I never let him forget. "Hey Scott how's it going?" he had a REAL evil spark in his eye and grin on his face.
"Looks like you got your hands full buddy...".
At that he ran his hand up my side tickled my armpit. I didn't move or react because I knew it was coming. Guy says anyway, "FUCK your not Ticklish big guy are ya?". I was a dead man. He got me laughing a little with his stupid ribbing at my pride. His tickling of my armpits and upper body started to get to me. He saw it and wasn't about to let up. He just grinned at me and focused tickling below my biceps at the top of my armpits.
I started cursing the guy out, laughing a little, trying to get a better grip on the fixture. "Hey Scott, its a good thing we got a tough guy like you holding up those heavy, expensive fixtures...not too heavy are they?" as he dug one hand into my abs.
That was it, I was laughing. The guy had me sweating for a good 10 minutes. He only stopped when he saw I was starting to lose my grip. I had it coming. He was pretty tough so I got on his nerves about how 'small' he was all the time in fun.