Not a "famous" Youtuber, but one I loved and respected at the time. Halo 4 was coming out, and I was gearing up for it. I bought a new Xbox 360 (old one died), got a new Xbox Live account, and played some good ol' Halo 3! I sucked at it of course, having grown up more on Reach, but I loved it. I was amazed to find that the youtuber I was following at the time, who inspired me, was in a game with me! 

it's a 6:10

X BR GUY is also the name of my PSN. So cringe, wish I could change it. 

I want to face DSP in USFII and just spam buttons and see him get pissed off.

Ah, in game. In that case, not really, but I have met a few in real life. Those were surprises to me xD

I got to play Mario Kart 8 against Chadtronic one night. He got 5th and I got 6th.

No but to semi relate to the op and the Halo post...I played some of the developers at Bungie in Halo Reach...I know it doesn't count...it just reminded me of it.

This would never be something I care about. I met HipHop Gamer in real life though.

I remember last year I was on Rocket League and I had somebody on my team (I can’t remember his name) then everybody was hassling him and really excited about who this person was, but I didn’t have a clue as I don’t get that involved in YouTube. Anyways it turned out he was a “famous” YouTube streamer.

Played with Karmakut in Squad, not surprising tho since he is a Squad Youtuber and I was playing on his server of choice. Was fun, he was my Squad leader and we just won that match.

This is cooler to me than playing some YouTube "star" douchebag.  

lol I wish Sony would allow us!

And like you I haven't played against a youtuber but I've matched with pros in Halo.

Heinz and Str8 sick in Halo 4, recently in MCC Dersky and Naded (Naded was on my team twice)