Reply to post: And some more:

And some more:

GPGMail / GPGTools: GPG implementation for Mac, including email signing + encryption. Beta for Yosemite currently, but reasonably stable. (I believe it is changing to requiring a payment, though)

Handbrake: for ripping DVDs / converting videos (potentially requires VNC too; I can't remember)

Chicken of the VNC: VNC client

Isolator: for keeping just one window in focus, without using full screen mode

MacTheRipper: DVD ripper

photorec: Unix command line recovery tool, great for recovering photos, documents etc. from USB or memory sticks

Telephone: nice SIP client with address book integration, but does not support encryption :(

Transmission: BitTorrent client, for downloading those Linux distributions