Yeah, ok I have a thing for when people suck on the other's fingers. I mean not just to get them wet but as a thing they like to do. Like a habit, a calming mechanism, a taste thing, etc. It's sexy, suggestive and kind of adorable at the same time :P

Due South
Scrabble by Speranza -
Not really about this but includes a scene where Fraser sucks on Rayk's fingers while getting a blow job. It's actually wonderfully plotty and interestingly it's told from the first persons point of view for both guys (at the same time!) really you need to see how it's done, a bit trippy realding it a first but well worth it.

House
Threesome Verse by alex51324 . In which Chase/House/Wilson are in a threesome with decidedly D/s tones but not all that much hard-core kink. It's kind of sweet actually. Chase is a little childlike in this fic but that adds to the charm plus he really likes to have something in his mouth. (she has another series called the Relationship Verse which features a similar oral interest from Chase as well)

Torchwood
A Close and Holy Darkness by </a></b></a>spiderine  - Sub!Ianto/Dom!Jack
Avery hot not-really-kissing scene on the roof in this series where basically Ianto gets to make out with Jack's fingers instead of his mouth.