When I was younger I memorized this in three (3) steps to use at zero (0) family gatherings... is it cheating if my stupidest joke is the only one I can recall instantly? :]

Warning: this joke is so ancient, it's sepia-toned.

An engineer and a doctor were arguing about who had the harder job. To prove his might, the engineer decided to open a clinic, betting he'd be a successful doctor:

"If we can cure you, you pay $500; if we can't, we pay you $1,000."

Of course the doctor saw the proverbial button immediately. The guy didn't even have a license! So the doc went straight to the clinic as his first patient.

Doc: "Sir, I have lost my sense of taste."

Engineer: "Nurse, please bring the medicine from box 22 and put 3 drops in the patient's mouth."

Doc: "Blawrgh! This is gasoline!"

Engineer: "Congratulations! You've got your taste back. That will be $500."

The doctor leaves, fuming. But not to be beaten, he goes back after a few days -- he can still leave with a profit if he plays this right.

Doc: "Sir, I have lost my memory."

Engineer: "Nurse, please bring the medicine from box 22 and put 3 drops in the patient's mouth."

Doc: "What, no! That's gasoline!"

Engineer: "Congratulations! You've got your memory back. That will be $500."

The doctor leaves pissed. Buuut, doc comes back after a few days

he needs to at least break even, right? So, more determined than before, he brings a cane and says:

Doc: "Sir, I've gone blind."

Engineer: disappointed "Well, unfortunately I don't have any medicine for that. Take this $1,000."

Doc: "But this is $500..."

Engineer: "Congratulations! You've got your vision back! That will be $500."