I've always liked tickling for as long as I can remember. My earliest memory is of a scientist that was tied to a rack with a feather wiggled over his soles, his toes flailing. At least that's how I remember it.
I will say, though, that while I always enjoyed tickling, and even obsessed about it, every time a female character was tickled, I'd get uncomfortable. Like, I enjoyed it, but I didn't like that it was happening to a female.
( And now that I know I'm a flaming queer, it makes so much sense now :3 )
I remember that there were many characters that I really wanted to see get tickled, but never happened. Launchpad from the Mighty Ducks cartoon, King Koopa and Buffshell from the Super Mario Brothers Super Show, Godzilla from the cartoon... I'm sure the list could go on if my mind would work properly, lol. I've also always preferred monstrous or non-humans being tickled to humans being tickled...
...which is probably the entire reason I became a furry.
Mostly the monsters. The bigger they are, the harder they laugh.