My worst tickle spots are the most private! My labia has an outer rim that is so ticklish inside I just about scream...but people don't seem to be able to find it...hehehe my secret spot.
The labia are also extremely sensitive. Tickling there makes me squeal...heck people wiggling fingers at the bare pussy makes me laugh. My clit is also EXTREMELY ticklish. The inside vagina is not ticklish, however.
I used to get embarrassed about being ticklish "down there," when I was younger. Guys were usually confused when I'd burst out laughing when they would open the labia, or touch the clit...
It is so ticklish that I immediately try to close my legs, anyone headed down there is in for some giggles. I have never been tied with my legs open and tickled there, but want to do it one day. Honestly I'm a little scared though because it tickles so freaking much.