-Writing Scripts? There is Pages (the Apple Word Processor), Office for the Mac (I'd wait till the new version comes out), Scrivener (which I got for NanoWriMo completion at a discount). That is, I assume, the 'movie/play scripts bit' not programming script (which you'll have to ask someone else about)
-iMovie comes with most Macbooks and you can do a lot of editing with it, and there is a couple free/cheap programs out there to edit (or you can go full on crazy and something like Adobe movie editing software Premiere)
-Games: This is the weak point of the system but you can play CoH/V, WoW, Eve Online (my 3 MMOs), and Steam is adding a TON of options over time (they just finished their free Portal weekened)