When one is looking for a username, one may want to be unique.
Some ideas to create a unique username:
• Try not to add numbers, being MinecraftGirlForever448897 just isnt going to work.
• Add something that describes you, or your favorite thing, "HappyRain"
•Don't push it with, "HappyAlwaysLovingRain"
•Remember, if you feel confident about your username, others will too!

Examples of usernames I like: 
JayminGames, Widget4Life, alegoguy253, AnimedDonut, 10enderdragon

Remember. this is %100 my opinion and I do not intend to offend anyone.