I am a really ticklish person so I was curious as to what caused some people to be extremely ticklish (me) and others to not be ticklish at all. I found out there two different types of tickling: knismesis, a light tickle or itching sensation which doesn't cause laughter and gargalesis, which highly sensitive areas are tickled causing laughter. You also can't tickle yourself, you can only cause knismesis by touching the roof of your mouth with your tongue.
i found a lot of information one these sites:
i also found this really cute video of a penguin being tickled