Mario Party 9: When Beta, Gamma, and Alpha kick eachother off the platform simultaneously in a minigame, giving Delta a win.
Mario Party 2: Shy Guy Says, Alpha recites a line from Courage the Cowardly Dog. One beat later, Beta gets in on it, much to Alpha's joy- only for Alpha, Beta, and Delta to get the flag wrong at the same time.
Ultimate Marvel vs. Capcom 3: A few, but the best would be the epic fail in the battle between Liam and Tom. While Tom used Felicia's Level 3 Hyper, Liam accidentally used Wesker's Rhino Charge. Both of them were out of range, but then Liam decided to DHC into Vergil's Devil Trigger and rush straight into Felicia's hyper, killing himself in the process.