Funny, but I was having a conversation with co-workers about the overuse of the word "Gentleman."
One of my pet peeves is listening to a victim testifying in court about how she was attacked, and still describing the suspect as a "Gentleman!" As in, "Then the Gentleman forced his way inside my house and started attacking me."
GAHH!!! THAT'S NOT A GENTLEMAN!!!!

I did, however, find this list. It is not intended to be all-inclusive:

Rules of a GENTLEMAN

1. A Gentleman is always presentable.

2. Live a passionate life, with a compassionate nature, and dispassionate judgment.

3. Talent is God-given. Be humble. Fame is man-given. Be grateful. Conceit is self-given. Be careful.

4. Opening the door for a lady is not optional.

5. A Gentleman is one who puts more into the world than he takes out.

6. Nothing beats a good hat, so long as it is removed when indoors.

7. Anything worth having, is worth working hard for.

8. A Gentleman will never instigate a fight, but he is permitted to end one.

9. A Gentleman reads and reflects.

10. The best suits are tailored (ties should never be a focal point).

11. A Gentleman means what he says, and says what he means.

12. Be gracious in manner, humble in tone, and thankful for what is given.

13. A Gentleman lives beyond his zone of comfort.

14. The line between confidence and arrogance is very thin, and a Gentleman is aware of it.

15. Drinks are not meant to be mixed.

16. A Gentleman can drive stick-shift.

17. A Gentleman can jump if need be.

18. Know the differences between courage and stupidity.

19. A Gentleman is observant, and takes action without delay.

20. To a lady, A Gentleman will readily offer both his coat and his hand.