Chuck: The latest Wham is in Season Four when Timothy Dalton's character reveals himself as the Big Bad of the season, Alexei Volkov.
When Jill is revealed as a baddie in "Chuck vs. the Gravitron," though as she is the ex-girlfriend, some people may have seen this coming.
Don't forget the episode when Morgan finally finds out about Chuck. Or when you find out that Casey has a daughter. Or when his father is killed while Ellie is watching from the shadows. Or hey, the first big wham when you find out Chuck's father is Orion, and after that when Chuck downloads the intersect 2.0 and takes down a group of bad guys with his new powers.
Chuck vs The Subway. Daniel Shaw really is alive! And there are so many Ring operatives inside the CIA that he is literally able to march into the middle of a debriefing, after having been revealed as a traitor, and everyone accepts what he says as truth. He shuts down the Intersect Operation, including having Sarah, Casey and General Beckman arrested, and chuck and his father have to go on the run. Even better because the line that really shows how screwed they are doubles as a Wham Line, when Shaw enters the debriefing.
But probably the biggest wham came in Chuck vs The Push Mix, in which:
But wait! It was Chuck himself all along! A plan which resulted in Volkoff playing right into his hands!
And then Chuck proposes to Sarah, who appears to accept.
In short, pretty much every ongoing plot thread in the whole frickin' show is tied up in 42 minutes flat, as no-one expected NBC to renew the show for Season 5, or green light any further episodes for Season 4. NBC gave them another eleven episodes halfway through the season.
The actual Season 4 finale, Chuck Versus the Cliffhanger has its own share of wham-tastic moments, including:
Chuck quitting from the CIA's employment in order to save Sarah, who had been poisoned.
In relation to the above, the CIA's representative has the Intersect removed from Chuck.
Chuck and Sarah get married...
...and start up their own spy business.
But apparently, there's a larger conspiracy at play, as Chuck learns from the CIA representative.
Did we mention that Morgan now has the Intersect in his head by episode's end?
In Season 5, the 2nd episode, Chuck Versus the Bearded Bandit, we get one hell of a Wham in the form of the Intersect not functioning appropriately in Morgan's head, causing the guy to lose sight of who he is.