Very fun thread idea!
Black Mirror - I've been a big Charlie Brooker fan ever since he did ScreenWipe, and this anthology series is the darkest show I regularly enjoy. Verging on emotionally harrowing rather than visually disturbing, a lot of the episode plotlines can really stick with you after the episode has ended (I still cant rewatch The National Anthem).
Parks & Rec - The most recent addition to this list, I've been hooked on the upbeat nature Parks & Recs brings, something you would rarely find with this type of "awkward" comedy. The ensemble cast is incredible, each person has a different charm and they all play off each other really well.
It's Always Sunny - On the flipside, Always Sunny is just as funny but insanely pessimistic, a wonderful contrast to Parks. Whilst it has become a little more hit and miss in recent times, the show is consistently clever and when a joke lands, it lands hard.
Taskmaster - Without a doubt, this is the one show I think everyone should watch. Five contestants (usually comedians) compete in a series of eccentric challenges, all requiring some creative thinking, and all utterly absurd (e.g. "Make the best snowman (in July)", "Get a basketball through a hoop without touching it"). It's the funniest thing on TV and I adore it completely.
Only Connect - I fear OC has peaked in recent times, honestly, but I still adore this intensely puzzling quiz show. Teams are given a series of 4 clues, one after another, attempting to figure out the common link between all of them. It is potentially the hardest quiz show aired on UK TV. Marvelous stuff.