I identify as a lesbian and all my fantasies involve being tickled by a woman. 🙂 Even when I identified as an asexual straight girl, my tickle fantasies have always remained consistent. And yes, like JerryB said, I think your arousal had way more to do with your fetish than the fact that it was a guy doing it to you. True, it is rarer that male 'lees and 'lers venture beyond playing with the sex they're attracted to, but it does happen (and this problem doesn't exist in male bisexuals, of course). But no, I wouldn't worry about your sexual orientation changing because of this experience. If you don't see yourself doing sexual acts with a man or being in a relationship with one, you're still the same straight male ticklephile as usual. 🙂