I look for accidental tickling in massages frequently, either feet or upper body. They are extremely rare. It seems that people who are very ticklish just don't get foot or regular massages, and even less have them videoed and uploaded to the internet. However, there are some gems, many of which are on the channel that Heimlick linked to above.
This is an absolutely brilliant one from that same channel that that's on vimeo, not youtube:
https://vimeo.com/ 269232930
30:42-33:00
Here's another with the same gorgeous woman. I forget where he gets her here, it's usually in her hips and sides and underarms. This chick is adorably ticklish:
https://vimeo.com/ 269234041
As far as accidental tickles though, this one is far and away my favorite of all time:
https://www.you tube.com/watch?v=FAaJnHMqmw4
There's no audio but you don't even need to hear it to see how unbearably ticklish this chick is on her upper outside thigh, leg, and then she goes absolutely ballistic when she's having sole of her foot worked on. I imagine that she was laughing so loudly that they said "let's just play music over it" ha ha. And the best is that it's confirmed that she was going nuts because she was ticklish on her foot in the comments.
I search all the time to find something better than this one and have yet to find one.
Anyone else looking and find anything in this awesome awesome category of accidental tickles not listed already?