Andy breaks up a Hatfields and McCoys (or Montague and Capulet, considering that their kids want to get married) style feud by pretending to arrange a duel between the two crusty old guys. Neither one of them wants to actually shoot the other, and when Andy fires a shot into the air both of them run for it. He gets them together later, pointing out that their kids don't care what their parents think, they love each other.
Andy: Why, you mix these two fine bloods together here and you two old buzzards are liable to get yourselves a grandson that can't be nothing in this world but a natural born hero! Why, yes sir! Why, you let these two young'uns [stops as both men point their shotguns at him]Now what is it.
Buzzard 1: You just stop the blabbering, sheriff, and get on with the marrying.
In the first scene of the very first episode, we get this gem. Andy (serving as Justice of the Peace) is marrying his housekeeper to her sweetheart. When Opie (who doesn't want her to go) starts making a scene, she offers to stay behind for a few days.
Andy: "You can't send Wilbur off on a honeymoon by himself. That'd be like putting a pig in a sty and taking away the mud."
Groom: "...Seems to me there's something wrong about the way you put that."
In one episode Barney buys an army surplus motorcycle and proceeds to wreak havoc on the town. Andy finally convinces him to give it up. Then, at the end of the episode, he gets the news that Barney has gone to another army surplus auction. Cut to Andy pulling over an armored personnel carrier. Except it wasn't Barney this time. Cue Andy having to explain to an irate Army Officer why he thought his deputy might be driving a tank.
In one episode Barney thinks Andy and Helen are engaged and has arranged a big surprise party with Aunt Bea for them. In order to get them there at the right moment, Barney and Thelma Lou invite them out to dinner and keep making up increasingly flimsy excuses to delay them until the right time:
Thelma Lou: "I don't like spaghetti."
Helen: "Thelma Lou, we had spaghetti for lunch last week and you told me you loved it!"
Barney: "A lot of people lie at lunch; what of it?!"
When Barney is shocked to learn Helen plans to keep teaching after she marries:
Andy: "A lot of women do that, Barney; this is the twentieth century."
Barney: (stiffly) "I know what century it is."
In "Ernest T. Bass Joins the Army", Barney tries to keep Bass from throwing a rock at the replacement window for the sheriff's office. He then hits the glass with his gun and smashes it himself.
Any time Barney accidentally fires his gun while handling it.