My all time favorite (which for all I know is the legal equivalent of "why isn't my computer working? Oh, the power's out" that IT people hear all the time), so apologies if you've heard it a million times-- was the guy accused of robbery who fired his lawyer and did an otherwise fairly competent defense of himself. Problem was he could not get the clerk to budge on his story or identification of him, and remarks, "I should have blown your (expletive) face off" *realizes where he is* "If I'd been there!!"
"If fighting is sure to result in victory, then you must fight! Sun Tzu said that, and I'd say he knows a little bit more about fighting than you do, pal, because he invented it, and then he perfected it so that no living man could best him in the ring of honor. Then, he used his fight money to buy two of every animal on earth, and then he herded them onto a boat, and then he beat the crap out of every single one. And from that day forward any time a bunch of animals are together in one place it's called a zoo! (Beat) Unless it's a farm!"