1. Documents 2 because it offers enables the iPhone with office capabilities such as editing google docs and uploading the changes, transfer files over Wi-Fi and has a sound recorder.
2. Defend your castle because it is fun and addicting
Gamestop has the silver version for 54.99 which is the cheapest that I have seen (Yesasia.com has the import version for 59.99)
http://www.gamestop.com/Catalog/ProductDetails.aspx?product_id=74491