Alfred - Launch/do almost anything. 
Caffeine - Keep your Mac awake. Pretty menubar replacement found here.
Bowtie - Controls iTunes.
Remind Me Later - Add events to iCal quickly without opening up the app.
Skitch - Fast screenshots, use it mostly for the notation feature.
Droplr - Short URL sharing/screenshots tool.
Dropbox - Sync your files.
Divvy - Window management.
Evernote - Notes, save anything.
Transmit - Best FTP client ever.
Littlesnapper - Snaps, mostly used for saving inspiration.
Facebook Notifier - Notifies you of Facebook activity.

(From Adelle Charles, Founder of Fuel Brand Inc., Carbon Ads & Tinder. You can catch me here.)