I recently went to watch the film 'Heartbreakers', with Sigourney Weaver and Jennifer Love Hewitt (spelling?). Anyway, apart from being a very funny movie, there is a short scene in which Weaver is demonstrating to Hewitt how to fall properly. She trips her up, then they have a brief tickle fight in which Weaver tickles her belly and she squeals and laughs. It only lasts a few seconds, but it's very nice. Check it out if you can.