Masturbation is a necessary thing for many when you don't have sex at your disposal. I also view it as different than sex itself, so I view it as normal. I am guilty as is 95% of this forum, I bet.
A tickle fight or session with your GF would also often result in cumming, so why not? It's just a human nature to want changes and to experiment.
I remember when the tickling forums were new, people were almost all grossed out by the thought of tickling someone until the 'lee wets herself/himself. Nowadays it seems fantasy no.1 of the tickling community (the intensity beats the grosness; it's just so erotic to do stuff you would never think of doing with someone else, because you respect the body of your significant other).