Best joke you've heard

[golf_cart_john]

What's the best joke you've heard? It would be preferable if it's something uncommon, and the moderators probably don't want to see anything off color. Here's my best, at least recently:

Dr. Schambaugh, of the University of Oklahoma
School of Chemical Engineering, Final Exam for
May of 1997 consisted of only one question. Dr.
Schambaugh is known for asking questions such as,
''Why do airplanes fly?'' on his final exams. His
one and only final exam question in May 1997 for
his Momentum, Heat and Mass Transfer II class
was:
''Is hell exothermic or endothermic? Support your
answer with proof.''

Most of the students wrote proofs of their
beliefs using Boyle's Law or some variant. One
student, however, wrote the following:
"First, we postulate that if souls exist, then
they must have some mass. If they do, then a mole
of souls can also have a mass. So, at what rate
are souls moving into hell and at what rate are
souls leaving? I think we can safely assume that
once a soul gets to hell, it will not leave.
Therefore, no souls are leaving. As for souls
entering hell, let us look at the different
religions that exist in the world today. Some of
these religions state that if you are not a
member of their religion, then you will go to
hell. Since there are more than one of these
religions and people do not belong to more than
one religion, we can project that all people and
souls go to hell. With birth and death rates as
they are, we can expect the number of souls in
hell to increase exponentially. Now, we look at
the rate of change in volume in hell. Boyle's law
states that in order for the temperature and
pressure in hell to stay the same, the ratio of
the mass of souls and volume needs to stay
constant. Two options exist:
1. If hell is expanding at a slower rate than the
rate at which souls enter hell, then the
temperature and pressure in hell will increase
until all hell breaks loose. 2. If hell is
expanding at a rate faster than the increase of
souls in hell, then the temperature and pressure
will drop until hell freezes over. So which is
it? If we accept the quote given to me by Theresa
Manyan during Freshman year, ''that it will be a
cold night in hell before I sleep with you'' and
take into account the fact that I still have NOT
succeeded in having sexual relations with her,
then Option 2 cannot be true. Thus, hell is
exothermic."
The student, Tim Graham, got the only A.