This is a tough choice!! I had to do a top 10. My lists are never in order, so this is random.
Buffy & Angel
Angel
Buffy the Vampire Slayer
It's the first time they kiss & the first time that I'm like, "Augh Buffy & Angel!!!"
(can't find an actual video of this kiss alone, but it happens about 35 seconds into this video - and I hate the song in the video by the way)
Ross & Rachel
The One Where Ross Finds Out
Friends
It's just a major "finally" moment!! Theirs is an epic romance. LOL
(yeah I can't find a picture of this one)
Lexie & Sloan
All By Myself
Grey's Anatomy
They are my favorite Grey's couple & I got really excited when they got together! I like it that Mark goes from being a bad guy to a good guy with her.
(the scene is about 2:30 into this video)
Bones & Booth
Santa in the Slush
Bones
Even though there wasn't really much to celebrate here - no relationship, no confirmation that they like each other - this was still really exciting because you could kinda tell that they secretly love each other. We're STILL building toward a relationship 2 years later, but still. It was exciting.
(only the first 15 seconds were actually shown in the episode)
House & Cuddy
Help Me
House, MD
I think everybody has been waiting for this since the beginning of the show. House & Cuddy finally, legitimately & lovingly getting together was just the best thing ever in the show!! I loved it!
(3:50 mark)
Sawyer & Kate
There's No Place Like Home, Part 2
Lost
This is when Sawyer kisses Kate before jumping off the helicopter to save everyone. It was hard to pick one kiss of theirs that is my favorite, but I like this one because you see that Sawyer has changed & that he loves Kate.
(2:00 mark)
Jim & Pam
Casino Night
The Office
Who didn't love it when Jim finally kissed Pam after he told her he loved her?? Oh my gosh I was so excited!!! I also really like when he kisses her when they find out she's pregnant. That scene was one of the best scenes ever in TV in my opinion.
(2:30 = casino night,
this video has the other one at the 2:50 mark)
Seth & Summer
The Rainy Day Women
The O.C.
This is just plain fun. I loved Seth & Summer & this kiss is just cute! And it's when they finally get back together!! You gotta love it.
Nathan & Haley
The Wind That Blew My Heart Away
One Tree Hill
The kiss where they're in the rain & Nathan is getting all of Haley's newspaper clippings to show that he was still proud of her even though she left him to go on tour. I just love it. You know that they're going to be okay!!
(2:30 mark)
Buffy & Spike
Intervention
Buffy the Vampire Slayer
The one at the end where Buffy is pretending to be the Buffybot to find out if Spike told Glory who Dawn was. I know this is a weird one to pick, but it's the first time Buffy kisses Spike on purpose because she thinks he deserves it. Something about it has just always stuck with me. I probably watch it like 3 times every time I watch the episode.
I've already thought of about 4 more that I could add to this. Oh well.