It depends entirely upon you - your age, your gender, your size, whether you have friends or family who would go along with you and make a group costume or not.
TV and Movie characters are always good for Halloween, as are video game characters or comic book characters.
You could also do a funny costume like a hotdog or pop tart or piece of candy corn.
The old stand-by costumes are witch, mummy, vampire, or zombie, of course.
I believe the best place to get a halloween costume is from Party City.
If you are looking information on what would be a good alien costume for Halloween, the best site is on costumezone.com/, they will give you the best costumes.
Part city
the headless horseman
If you are looking for more information on where can you find a cheerleader costume for Halloween, the best place to look is on www.costumecraze.com/Traditional-Costumes-Cheerleader-Costume.
Probably ghost costume. Or ghost detector
There are literally dozens of different halloween costumes available for your son. One of the best costumes is actually the costume of a cowboy.
moster high
I think that it would be a ballerina. Or a bumblebee.
As long as it is not past Halloween, it isn't too late to get a costume. Costume stores are open on Halloween and days before.
During the Halloween season, I find the best place to go for costumes with the biggest selection is Party City. They transform over half of their store into a Halloween costume showcase.
Umpire is a Halloween costume. It begins with the letter u.