The end of Frontline's "Operation Rapunzel" level requires you to "motivate" the resistance operative you've rescued, as he's reluctant to make a three-story leap of faith. What's the preferred motivational method of hard-bitten commando Jimmy Patterson? Shove him off the roof.
PANZERKNACKER UNLEASHED. Dancing dogs, that is all.
Frontline had that Mockumentary that was pretty hilarious
Not really a Crowning Moment of Funny, but in the first game when a level briefing (by female resistance fighterManon) states "I asked an old boyfriend (which is x-ed out), er, male acquaintance of mine to..." You can almost see the veteran commando blushing.
Also the first game's ending, where you launch the sabotaged V2 rocket. The scientists' responses are priceless. Below is a translation to what the scientists say...
...abort the start! I repeat! Abort start!
Control room here, all of our control panels are broken. The start of the rocket can only be aborted at the starting ramp. Hurry!
Abort start! ABORT! Abort ignition!
10, 9, 8, 7, 6, 5, 4, 3, 2, 1!
Abort! Abort start!
Everyone get out of the building!
RUN FOR YOUR LIVES!
We're going to die!
It's coming down on us—
(After the explosion)
The American... has won...
Frontline has a pretty funny Lampshading of Jimmy Patterson's Heroic Mime status. The level opens with a superior officer saying "...so how about you disarm a few of the bombs on your way across the bridge? [Doesn't pause.] "I'll take your silence for a yes. Go get 'em, sport."
Frontline's dev team definitely had a sense of humor. One mission begins with you stealing a German officer's uniform and papers. When you're stopped by a guard, you show him your papers and he waves you through...despite the fact that there's a giant wanted poster with your face on it not three feet behind him!
A rare one in Warfighter. After shooting your way through a terrorist training camp and finding a cache of high explosives, Voodoo casually mentions there's enough there to blow the mountaintop off. After he's done discussing his mission plan with Dusty, he starts to give orders to the squad, only to find they've all scarpered.
In the Nijmegen Bridge level of Frontline, you can climb to the top of the bridge, which leads to the German sitting on the side turning around to see what happened and falling to his death, and the German sniping on the center platform will attempt to shoot you, only to find that his gun is jammed. So he stands up, puts his hand on his helmet, and jumps off.