A man gets home early from work and catches his wife in bed with another man...
The husband challenges the other man to an old fashioned duel with his hand guns, whoever manages to shoot first and kill the other gets his wife. The other man agrees, so they go into another room so the wife doesn't have to see it. Once in the other room, the husband turns to the other man and says:
"Why should either of us have to die? We will both fire a shot into the air and lay on the ground as if we're dead, when she comes in she will see our 'lifeless' bodies and rush to one of us, whoever she chooses can have her." The other man agrees again, so they fire into the air and collapse.
The wife throws the door open and peers down at the two men, then backs out of the room and calls out: "Darling, you can come out! They're both dead!"