This cheat will change the sex of your target (if they're male, this command will make them female and vice versa). Use 'player.sexchange' to change the sex of your character.
sexchange Target Command
If your target is female, the above command would make your target male. If your target is male, the above command would make your target female.
This console command does the same as the first example, but to your character (not your target).