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If you like games that without a lot of action in them, I would suggest Braid (one of the most creative platfomers there is, only around $3 for a limited time!) and And yet it moves.
 
asking what the best App is is like asking who's the prettiest girl. It depends on needs and desires. Ask 5 guys who's the prettiest girl in the room and you may get 5 answers, ask 5 guys who's the ugliest and you'll likely get only one or two choices ;)

I have iWorks (purchased before the App Store on disk) and last week I bought Aperture from the App Store which is currently rated in the top 10 paid Apps and #1 top grossing app. But that means nothing is you don't want or need it
 
I downloaded three really useful things from the Mac App Store- all free.

Stone Hill Time Card- great for keeping track of my time, and simple enough to keep doing it (key point for me.)

Evernote- because Evernote is awesome for remembering things, and it helps keep my bookmarks menu clear of stuff I eventually want to return to. :p

iProcrastinate- I had the original free iPod version for a while and found it useful for its ability to have lists in different subjects (jobs, clients, whatever). The free Mac app and the new iOS version (paid) sync together as easily as the developer claims- much appreciated.
 
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