NomadBSD

Just installed NomadBSD [1] to an old USB stick after reading
about it on ItsFoss. It's pretty snappy even on the old drive
I'm using. The default theme is pleasing and the default
application list is very complete (perhaps too complete).
If I had a criticism it might be that they should leave more
packages out and let users install them. Since it's based on
FreeBSD, all the FreeBSD packages are available. Git is even
installed by default! The window manager is a customized
version of openbox with a Mac-style app bar at the bottom.

The graphical setup tool allows for customization of
default tools like the file manager and editor. I went with
Vim (of course) and Pcmanfm (a nice, lightweight file manager
typically found on LXDE installations).

One of the unexpected benefits of playing around with NomadBSD
is the exposure to some lightweight apps I had never heard of
such as Asunder CD Ripper and Deadbeef Music Player. I'll
definitely be installing those and giving them a shot on my
Lubuntu daily driver.

If you want a BSD thats optimized for USB stick usage, I'd
recommend NomadBSD!

[1] http://nomadbsd.org/