The end of the episode "Blind Spot". When Michael pulls the villain out of his wrecked car expecting him to try and fight back (like they always do). Instead, just as he pulls back for the punch... the guy falls over backwards. And the look on Michaels face says "Well, that was rather anticlimactic."
Also counts as a moment of funny.
The finale of "A Good Knight's Work" When KITT slams into an apartment window... three floors off the ground!
April: You might as well know what I think about you and your destiny. Your destiny is to never have a woman who wants you for yourself. Never have a man who respects you for what you are. Your destiny is death. And if you don't believe me just go take a good look in the mirror. There are holes where your eyes should be. And behind them there's nothing but blackness.
In "No Big Thing," Devon is arrested in a small town on bogus charges. He overhears his cellmates talking about breaking out and offers to come up with a solution, if they let him come along. When it's pointed out that he "doesn't look like the prison break type," he agrees— adding that the SS thought the same thing, which allowed him to break out of two German prison camps in the war. His cellmates agree, Devon executes the breakout and even works in a Dukes of Hazzard leap with the getaway truck. This being a man who's, up to this point, been a very stoic, serious character.