As a couple have already said, games I'm playing or planning on playing, to this day I still haven't watched any videos of Murdered: Soul Suspect or Infamous: Second Son, although I'm starting to get a little lenient with Murdered.
Anyway.
And by the time I'm finished I really can't be bothered to go back and watch.
Sometimes I'll watch games that I've already finished seeing as, hey, I already finished them but sometimes that can be a hassle.
I have a friend who told me how frustrating it was to watch, I think he said it was Tobuscus, go through Portal 2 after he finished it, and I've watched a couple times while my sister was running through the same game, it's really frustrating; hence why I did my best to remove myself from the room when she played because I was getting upset and she didn't need that pressure, it was bad for both of us.
Anyhow.
Another hassle with games you've already played is that if you're good at them watching someone who's *not* good at them is a strain, and these next stories come from TheSw1tcher.
Watching Matt, Woolie, and Liam die over and over and over again in Metroid: Fusion to bosses that I can beat without getting hit once was a little exhausting. Don't get me wrong, it took a long time and many playthroughs to learn the boss's patterns but still.
Then there was Matt, Pat, Woolie, and Liam play each other in Mortal Kombat and not know how to do Fatalities. Once again, the safest way to make sure you nail them, holding block while putting in the directions then letting go to hit the button, can be tricky if you haven't done it a few times and really you won't know about that method unless someone tells you, I know I had to be told. But come on, Fatalities are the icing on a Mortal Kombat cake, how can you not do them?!
I, um, I seem to have answered this topic a little too hard.
TL;DR Games that I'm playing or will play and games that I'm good at.