I've always loved Murphy's Law truisms. These fare pretty well, too...
*Law of Close Encounters
The probability of meeting someone you know increases dramatically when you are with someone you don't want to be seen with.
*Law of Mechanical Repair
After your hands become coated with grease, your nose will begin to itch and you'll have to pee.
*Law of Gravity
Any tool, when dropped, will roll to the least accessible corner.
*Law of Probability
The probability of being watched is directly proportional to the stupidity of your act.
*Law of Random Numbers
If you dial a wrong number, you never get a busy signal and someone always answers.
*Law of the Alibi
If you tell the boss you were late for work because you had a flat tire, the very next morning you will have a flat tire.
If you change lines (or traffic lanes), the one you were in will always move faster than the one you are in now (works every time).
*Law of the Result
When you try to prove to someone that a machine won't work, it will.
*Law of Biomechanics
The severity of the itch is inversely proportional to the reach.
*Law of the Theater
At any event, the people whose seats are furthest from the aisle arrive last.
*The Starbucks Law
As soon as you sit down to a cup of hot coffee, your boss will ask you to do something which will last until the coffee is cold.