Accountant:
Someone who knows the cost of everything and the value of nothing.

Auditor:
Someone who arrives after the battle and bayonets all the wounded.

Banker:
A fellow who lends you his umbrella when the sun is shining but who wants it back the minute it begins to rain. (Mark Twain)

Economist:
An expert who will know tomorrow why the things he predicted yesterday didn't happen today.

Statistician:
Someone who is good with numbers, but lacks the personality to be an accountant.

Actuary:
Someone who brings a fake bomb on a plane, because that decreases the chances that there will be another bomb on the  plane. (Laurence J. Peter)

Programmer:
Someone who solves a problem you didn't know you had in a way you don't understand.

Mathematician:
A blind man in a dark room looking for a black cat which isn't there. (Charles R. Darwin)

Topologist:
A man who doesn't know the difference between a coffee cup and a doughnut.

Lawyer:
A person who writes a 10,000 word document and calls it a "brief." (Franz Kafka)

Psychologist:
A man who watches everyone else when a beautiful girl enters the room.

Professor:
Someone who talks in someone else's sleep.

Schoolteacher:
A disillusioned woman who used to think she liked children.

Consultant:
Someone who takes the watch off your wrist and tells you the time.

Financial Planner:
Someone who has less than 10% of your wealth but who can show you how to make money.

Diplomat:
Someone who can tell you to go to hell in such a way that you will actually look forward to the journey.