skymobiletv is great ont he ipad, its a fiver a month to watch skysports on your ipad and the quality is excellent. Prevents arguments in our house as the missus watches what she wants on TV and I have the footy on my ipad whilst still being sociable and sitting with her.
GarageBand is my fav at the moment, bloody brilliant for £3
the new SkyNews app is very impressive
iPlayer is excellent
For work stuff Pages Keynote and Numbers serve their purpose very well.
My most used app is called ghostwriter which I use to take notes in meetings etc as I can write on the screen as if it is a notepad.