Even though I'm a Team Peeta, the kiss that stands out to me the most is when Gale and Katniss are in the woods and he kisses her. Then he says, "I just had to do that once." and he dissapears. For some reason, I thought that was so sweet.
My favorite kiss was between Gale and Katniss after he got whipped. I think it was the first time she realized after she returned from the Games how much he meant to her, and how much it would hurt to lose him. It's like her eyes were opened seeing him so weak and hopeless. And i love that he remembered :)
I love all their kisses tho, the first was so heart breaking when he said "I just had to do that. Just once." and then runs off because he had to watch her make out with freaking Peeta the whole Games without knowing what hell was going on! Because i got hints throughout the first part of book 1 that he was into her, and to have to see the girl he's in love with not only trying to be killed but proclaiming her love for a boy she just really met. And i love the one in Mockingjay when they're out in the woods and they have to stop because she doesn't know where she is, haha. An she said it made her feel something, other than the mindless kisses (Except one) with Peeta, the ones that were all for show. That one gave me up but then it was torn apart at the end :(