College students: what are the apps that you use often? [OSX]

I'm new to OSX with a MBA 2013 and as far as getting work done on my mac, it's been iWork and MS Office. I was wondering what other productivity apps you guys could suggest? Could be anything really. From Evernote to...whatever it is that's making your college lives easier. Maybe some games too? (The most I play with yno. Steam. XD)

Thanks in advance! :)