In CHKilroy and Beagle's series of intertwining ARMA 2 videos, they grow into firm friends and share for a while, a brotherly bond. The death of one causes the other to exclaim in despair, or even go into a kamikaze rage. However, in a recent mission, Beagle accidentally proposed marrige to Kilroy, who said yes, affirming their heterosexual life partner status.
Spoony and Linkara give the distinct impression of being this in the instances where they interact, such instances being much more common for the two of them than it is for other Channel Awesome people.
In the series, The Nostalgia Chick and Nella are this; however, "My BFF, Nella" subverts the trope by revealing that their relationship is actually a business venture—the Chick pays Nella to look good and take her abuse.
Tucker and Church probably also fit, although to a lesser degree.
Alberta and Saskatchewan are this in the iammathewian project. Although whether there is evidence of it being a bit more romantic or not is up for debate.
Anthony Padilla and Ian Hecox of Smosh. Lampshaded at the end of the episode Replacement Needed; after splitting up, Anthony tearfully looks over a photograph of him pushing Ian on a swing, with the caption "Always and Forever...But We're Not Gay".
Strippin, In The Little Wood and Sparkles* from Area 11 form this during their time as the "Dream Team", livestreaming together many times and clearly enjoying being with each other. Strippin also has this vibe with Benji, his collab partner from Rail Bros; Benji may not be part of the Yogscast, but they're very good friends.
Jon and Arin on Game Grumps. These guys go together like salt and pepper, peanut butter and jelly, and any other heavy handed simile you can think of.
Then they broke up, and it became Danny and Arin.
Dexter Gilligan and Lyle Mc Douchebag of Sanity Not Included. At least up until the end of Season 3, in which Lyle commits suicide in the animated section of the show, marking his departure.
AmazingPhil and danisnotonfire who've lived together for years, work and frequently travel together. (Many fans disagree with the heterosexual part)