RoyalTSX, which does VNC and RDP plus ssh, and web, and is generally not a bad solution for logging into a bunch of remote machines with different access methods.
Xquartz, which lets me run X11 apps.
Serial, which is a decent GUI serial terminal emulator, for when screen isn't the right thing.
Parallels for VMs. I don't love it, but I haven't switched to anything else.
Carbon Copy Cloner for snapshot backups of my laptop to an external drive. It deals with encrypted, bootable, and recovery volumes.
GPG Suite, for secure email, etc.
OBS for screen captures, streaming, etc.
VLC for video playback.