Many actually come to mind
In Red Dead Redemption all of the textures suddenly disabled so every thing was its default model color, this sticks out as it was the first time I had encountered such a huge graphical glitch. Then a similar thing happened in Tomb Raider 2013 where i thought a cart highlighted in green was an in-game hint, except that after passing that point the game slowly began to break down as textures disappeared and random primary color gradients replaced them, At one point i was climbing a rope and wanted to check out that weird shadow pattern on Lara's face, turned put her face had become a checkerboard. I had to quit because the nearest cutscene devolved in to random colors and shapes making random movements.
I have no idea how I triggered it but I can only call what happened to me Horizontal Gravity. In Saints Row The Third I was playing coop with my friend and I got launched by an explosion when I hit a wall I just stayed there stuck to the wall and I could roll along it using the movement keys. When I rolled off the wall I just kept flying at a slow steady speed still in ragdoll and when ever I hit something that could block my progress it could roll on it and when I rolled off I continued to fly. Basically this caused my friend to have to continue the mission by himself and me to wonder what the hell was going on. And it only fixed itself once we failed the mission because he was killed and had to restart.
In Metal Gear Rising I was prolonging the prologue fight with Sam because I was pretty good at parrying, some how I managed to glitch him off of the train and had to wait for the hidden timer to run out to continue on with the fight.
And in, I think it was Dark Souls, I managed to glitch a hard enemy in to just standing still. I have no idea how it happened but hey, free kill for a difficult enemy that has a lot of souls.