Omnifocus 2 – Steep learning curve to use properly, but my life would be complete chaos without.
MsgFiler – If you have any kind of e-mail mailbox hierarchy, this is the ultimate time saver for filing.
1Password – Unless you want to use the same password for every site (don't!) a password manager is essential.
Motion – I have to do a lot of presentations in my professional life. Motion lets me look smarter than my competitors.
Keynote – See 'Motion' above. Make movies in Motion, drop them into Keynote.
Moom – Others have mentioned. Great window manager.
DropBox – If you regularly use more than one computer, this is a simple way to keep in sync.
SuperDuper and Crashplan – belt and braces. I'm old and I've been there. You WILL lose all your data one day. I'll be able to get mine back.
Office 2011 – For compatibility reasons I have to use Word. Couldn't live without it, but it's rough. Can't afford to risk a beta. Hoping 2016 is a nicer experience.