Colbert Bump / Newbie Boom: This happens to many of the independent games he plays, to the point that some developers have sent him beta builds of their games just to drum up excitement among the fans.
Milestone Celebration: He's made a couple videos for hitting a certain amount of subscribers, or at least thanked his bros directly.
He is a hugeRadiohead fan. His top five favorite albums are all In Rainbows.
Series Hiatus: Currently, he is putting Ni No Kuni and Kingdom Hearts on this.
Trolling Creator: He titled an news video informing viewers that he would be away on a business trip for a few days "Bye Bye Forever" and than opened it with him announcing his retirement before doing a 180 just to mess with the fans.
If Pewdie hadn't forgotten his Alice: Madness Returns save file when he moved, the series would probably have continued.
Why The Fandom Cant Have Nice Things: He eventually turned off rated comments because he was sick and tired of spam on the channel, though at first he left general comments on. (He later turned them off because he was annoyed with the Youtube overhaul, not that he was alone in doing that).
He also removed comments because of some trolls accusing him of beating his girlfriend. He was understandably unamused.