I'm not really a "favorite kiss" kinda girl. I much prefer platonic signs of intimacy rather than romantic ones.
So, I'm going to go with:
Ray Kowalski and Benton Fraser - underwater "kiss" in Due South's episode Mountie on the Bounty Part 1.
Because I've always been impressed with Paul Gross' ability to weave blatant fan-service into his story lines.
But seriously...I wish they had a category in this meme for "favorite instance of clothes sharing" or "favorite time people drank from the same glass" - because stuff like turns me on more than kisses.