Darren Criss

I was lucky enough to see Darren Criss for free(!) live at a festival in my neighborhood, a few years ago right at the start of Glee fame. I've been a fan since A Very Potter Musical and was excited, but I wasn't expecting such a great, varied performance. The repertoire ranged from Disney covers to jazz standards to covers made famous on Glee to his original music (which for me was the best part). Darren switched from guitar to piano and back; there was something for everyone.
It's got to be said that Darren is super sweet and charming, and is one of the more gracious musicians I've had the pleasure of seeing. He may be a star at this point, but he was down to earth and humble, and that was nice. He's also - as should be obvious from his theater and TV performances - got a ton of presence and had the whole crowd under his thumb whether getting everyone dancing or talking seriously about society.
At this particular performance we also got the treat of having Lauren Lopez (Draco in AVPM, among other more recent credits) up on stage to sing "Granger Danger". This made this super special but not unique - inviting Starkid and Glee costars to join in is a recurring feature of his concerts and is very possible if you're going to see him.
Would absolutely recommend, and if you can get to see him with a stand-up general admission sort of venue so much the better.