Sparrow is an email client for iPhone that takes a different approach to your inbox than the default/built-in Mail.app from Apple. It's inspired more by a Twitter client and feels very similar to using a Twitter app if you've ever used one.
It's on sale in the App Store this week - $0.99 on Tuesday and Wednesday, $1.99 on Thursday and back to its regular $2.99 on Friday.
I picked it up and am trying it out by using all my regular email accounts on Mail.app and putting my Lemon Productions account in Sparrow. My thinking is that way I can check work related stuff when I want to - or ignore it when I need to.
Don't be like Francis and miss your opportunity. :)