Tip Calculator

I know it's not very exciting, but since I have a crappy Verizon phone, which I only use for phonecalls, I don't want to pay for any apps.
There was a time when I used to pay for games, but that time has passed since I've got myself a DS.
I like the tip calculator, because it's very quick and easy to use.
You just have to enter the total sum, and it fills in a percentage for you (15%) which you could adjust.
Also, it give you an option to split among as many people as you'd like, which is a great feature.