Buffy and Giles was the first thing to come to mind for me! As is Faith and Giles (one of the only good things that came from the season 8 comics was their interactions. Fantastic scene where he grabs her and she kind of panics and stabs him with a fork. When he rolls up his sleeve to inspect the damage she sees his Mark of Eyghon tattoo and he says something along the lines of if she thought she was the only teen ever to rebel.)

I'm immensely irritated that Cordelia and Angel stopped being platonic because they were great too. :( I liked them better as friends than as romantic. PAH... I hate when that happened... it happened in Chance as well... Simon and Chance had the best friendship evar and then they had sex and bah... (Unfortunately that entire movie is just fuel to the kinda crazy Spike/Tara shippers... oh Amber and James... and Andy Hallett how you are missed.)

Let's see...
Veronica Mars and Wallace Fennel, actually their lack of romance was probably my favorite thing about them. They got to be awesome crimesolving team without any attraction between them.

Do Kara and Helo count? (Canonically they never had a thing but I totally believe that they got it on at least once back in the day. That sort of defeats the purpose. Who cares, I love them.)

Sarah and Casey in Chuck. Secretly? I ship Chuck/Casey more than Chuck/Sarah. But I'm down with them having an awesome spy threesome.

Ten and Donna in Doctor Who. Donna is just so different from Rose and Martha who do love... she's just so BAM!! In your face, and I think that's good for Ten.