The best glitch was in Red Dead Redemption: Undead Nightmare. Try your best to beat this.
Okay so in the opening cinematic when Zombie uncle is making his way to the house, there was something important that seemed to be missing, oh yeah, Uncle. For the darnedest reason, Uncle was invisible, so the game ended having these dramatic camera angles, suspenseful music and sexy Uncle groans and I was starring at the TV, confused out of my skull wondering what Rockstar were doing. That's only the beginning of this tale, I'm yet to get to the best part.
John kills Uncle after he bites Abigail and once the cinematic is over, Uncle,now on screen and visible finally, was a cougar all along. Yes, you read that correctly, Uncle was an invisible cougar. Abigail, who was bitten then turns into a Cougar (yes) who goes ahead and bites Jack and he... does not turn in a cougar, merely has the animations of a cougar. As those who have played the game, I now have to hogtie Abigail... except she's a cougar and you can't hogtie Cougars so I lose the mission, so I chase Jack and he runs off too far and I lose the mission.
This is the part where I realise because Uncle was an invisible, my wife became a cougar and my son thinks he was a cougar, I can't finish the game and that my dear readers is my entire experience with Red Dead Redemption: Undead Nightmare.