Best program that you can run on a macbook is windows 8.
trololololol
Transmission is a great, really simple torrent client. Logic is sweet if you like to make music. I use VLC a lot instead of itunes because it can play FLAC files.
Get the adobe cs6 master collection and Lightroom if you are into video/photo/design work. Also GeekTool if you want to add stuff like time and date on your desktop.