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My two cents:
(1) openSUSE for ease of installation, use, and KDE integration. The fact that openSUSE slowed releases to every 9 months, but even then won't release a version until it's ready is worth the wait.
(2) Fedora. Always had a soft spot for Fedora because every other version rocks.
(3) ChromeOS. Sure, it's Google, but with a Chromebox/book, it's really an extremely efficient little OS that constantly gets better. Just wish Google would make it easier to install on any other machine.
(4) Android. Closed, but its speed and simplicity are unbeatable.