Distinctly Feminine
Some females might want to display their sex with pride. In this case, look for names that have a distinct feminine reference. Ideas might include some of your favorite female movie characters, actresses or superheroines.
Female Associations
Many people associate certain animals or other elements with females. Integrating names of flowers or references to animals with a soft, cuddly personality with your real name can lend a feminine touch to your gamertag. Ideas might include "unicornwarrior," "psychorose," "towerofflower," "chickflix" or "damselindistress."
Word Plays and Symbols
Using word play can help you create individual female gamertags. Try word plays on famous male characters. "Pambo" instead of "Rambo" might work, especially if your name is Pam. Instead of Sgt. Rock, consider trying Sgt. Frock (as in a dress). Also, adding smiley faces using the colon and parentheses on your keypad can add a cutesy feel to your gamertag.
Ambiguous Gamertags
Some females might feel more comfortable not indicating their sex online for safety reasons, or simply to prevent being harassed or not taken seriously by some male players. Ambiguous names -- names that don't indicate your sex -- fit this purpose. If you play a lot of combat games, you might want to consider names like "nevermiss" or "gunpowderroom." There are many players on Xbox Live, so you might have to add numbers or letters to make a popular phrase unique, and thus, usable.