KT vs Tigers: I think KT has put up better performances, so just based on what we saw during the group phase I'm going to go with them.
FNatic vs EDG: I'm going with FNatic on this one. For one: they're a Western team so I have to at least stick with my hemisphere.
But beyond that I think that EDG has shown that they're fully capable of making a lot of mistakes. If Week 2 FNatic is the team that shows up to the Quarter Finals as opposed to Week 1 FNatic, then I can see them beating up on EDG pretty solidly.
Wolves vs Origen: This is my "toughest to call" game. Both teams have had their ups and downs so far, showing both brilliant moves and mistakes. I'll go with Origen, though, since Peke picked Anivia and that was one of my favorite games of the tournament so far. :3
SKT vs AHQ: Yeah, everyone already knows the outcome to this one. SKT is going to crush AHQ, as they've crushed everyone else. If AHQ somehow manages to beat SKT, I think we can safely call it the biggest upset in the history of League of Legends.