*thinks hard*
Hmm other than the traditional *tying up the current significant other* tickle torture. I think one of the best experiences for me was one night two of my very cute female friends and I went hiking together and afterwords went back to one of their houses and two of us ended up chasing the other, all around the house (We were teasing, before hand, "Hey we should jump her and tie her down and tickle her to death! That would be fun!" so yeah, on went the chasing, finally we managed to catch her and hold her down to the ground and took off her shoes and socks and (I had a few CAT5 cables in my laptop bag) tied her up and had much fun with her for the next 15 minutes or so. I took the feet my friend took her upper body and we occasionally switched off haha. We all had fun in the end though (of course I got it back just as bad later that night)
Good times ^_^