taptaptap, Tapbots, and Macheist have released a very well-designed calculator app for the iPhone and iPad called Calcbot -- it's available for 99 cents right now on the App Store. I would say that I don't know why we need another calculator app on the store, but this one's designed by Tapbots, so it's basically a clinic in UI design for the iPhone: clean and beautiful Retina Display-enabled buttons, gorgeous animations, a swipe-to-access extra set of functions, and the ability to go back and look at past calculations and even email them off. Basically, this is a calculator app you want to take a look at, even if you already have a calculator app.
Plus, Macheist is sweetening the deal as usual -- that 99 cent price is for a limited time only, and if you do pick up the app, you can spread the word about Calcbot on Facebook and pick up a free copy of the Socialite social networking app for Mac, which will allow you to manage all of your various social personalities all just one place. That's a $29 value right there, so you're basically making $28 on the deal -- excellent offering.