I've only just started watching these things, but the Zelda (LttP) one I watched just now was hilarious. Terrible framerate on the video, LPer wittering on about unrelated crap while being amazingly bad at the game, and spending a minute trying to make it look like Link was humping Zelda. All with hilarious commentary.
And the infamous Gaming in the Clinton Years where the guy suggested Eidos make a Tomb Raider game where Lara gets breast cancer. Just the "Oh my god he's serious!" from Diabeetus and Slowbeef was amazing.
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"I'm Commander Shepard, and you're standing in the biggest library in Citadel Space. Look me up."