During the opening credits of Cathouse the series there is a guy tickling a girls underarm while lying on top of her and she reacts very well. She seemed extremely ticklish. The scene lasted only a few seconds but it was top notch.
Awesome clip, toyou! I love the lady's quote (I think she's the one tickling the guy's feet, and she sounds so sexy when she says it), "...although when we were tickling him, he did get a boner!" And so did I when I imagined I was the guy they were tickling.