He outdid himself with his Mass Effectpapy grenier with amazing cosplay and the French Va of Joker, Female Shepard and Garrus.
And while we're on the topic of unexpected cameos, the Metal Gear review and the Anti Terror Force review both feature cameos by none other than Doug Walker, a.k.a. The Nostalgia Critic. Many jaws dropped on the days those videos were uploaded.
His fake trailer on a hypothetic My Little Pony film. He actually managed to make it EPIC.
Speaking of fake trailers, he also did one for a making-of in his second FAQ video. It's both hilarious and epic.
Ark Survival Evolved: Playing for more than 6 hours (for a 30-minute video) but finally, finally succeeding in taming and riding a dinosaur.
Ninja Hitler vs the Space Vikings, Fred's contribution to cinematic greatness in The Movies, consists mostly of Hitler getting his ass kicked by a woman and a man in a duck suit.
Fred finally, finally beating Tintin in Tibet. That the ending music of Gladiator plays over it doesn't hurt.