I've also just downloaded the new Guardian app (yeah, I know.................... ). However, the way it works and it's interface are just wonderful - allows off-line browsing and is very intuative to use
AnnoyATeen - emits a high frequency tone that'll annoy all the young 'uns around you. If you're old like me you won't hear it and if, like me, you work in a large open plan office you'll have hours of purile fun
PING - Cross between SMS and IM between other iPhones
NHS Drinks tracker - You log what drinks you've had and it telles you when you've had enough (bit like a wife really!!)
You must choose - A bit of fun when half cut
Password Keeper - What it says on the tin really