"The Outlaws," where Wes ups the ante on Kurt and Blaine's duet at Regionals. And their reaction when the duet actually happens:
Wes is still skeptical and everyone's still a little worried that Blaine will spring the existence of a Beatles-loving non-Kurt duet partner on them (which would mean one of the Warblers has fucking betrayed their own!), but then Blaine says there will be no auditions because he wants to sing with Kurt.
You know the Warblers are True Companions when they physically drag Blaine to a counselor. Wes and David especially treat Blaine like a little brother.
And when they not only notify school staff that Blaine has a stalker, but they start a buddy system to make sure he doesn't get in trouble.
The Warblers again in "Nikos." Wes and David force Alex to kidnap them along with Blaine. The minute Thad and Trent find out (thanks to David's cuff-links), they call the policeand the other Warblers. Their mass-text conversation at the end doubles as heartwarming and funny.