Knytt

[A Black Falcon]

*goes to Freeware Games, DOS Shareware/Freeware, and other pages in Tabworks, replicates most of the relevant parts of the list*

Old DOS freeware stuff: (some of these once apon a time wanted you to pay them if you liked the game, but the full game was available free - registering got you nothing more - and now they're effectively free. Some were always true freeware and said so.)
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Bananoid
Castle Adventure
Nethack
Llamatron
Star Goose
Castle Adventure
Arcade Volleyball
Tron
Viking Siege
Xerix
Commander Keen in Keen Dreams
Clyde's Adventure

Windows Freeware, Good to Great
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a7Xpg (dodge them... unique)
Torus Trooper (the awesome speed!)
Gunroar
Titanion
Noiz2sa
Tumiki Fighters (collect-the-enemy-parts shmup...)
Mu-cade
rRootage (these first eight are by the same author)
Warning Forever
Battle for Wesnoth (complex hex-based fantasy strategy)
Guardian Twins (sidescrolling adventure in Japanese. Language is a bit of a barrier.)
Natuki (great little platformer with an odd grabbing hook thing, try it!)
GLTron (best Tron Lightcycle game there is!)
Quine
Cave Story
Shooting Heart (To Heart fan-shmup, fun for fans, decent for others)
Gal Pani X (great Qix-style game, I've played this one quite a lot)
Sispri Gauntlet (cute but very hard Gauntlet-style game, great!) (this and the above are by same author)
The White Chamber (adventure)
Super Cosplay Wars Ultra (fighting game, lots of characters)
Dogma (somewhat incomplete but cool fighting game with some
yakouga v200 taiken (this and the three below are by the same guy. All bullet-hell shmups that sometimes run too fast but are great when they run normally.)
Hellbound
Sky (only one looping level, worst of these four)
Galshell
Renga Funsai Yuugi
Ahriman's Prophecy (action/adventure, much longer and more complex than most of these)
gr3ex (MSX Gradius remake)
Some Old Klik & Play Games: Bounce (a game I've liked for a long time), Dopefish Forever (Dopefish!)

Windows Freeware, Decent
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Other old Klik & Play games: Keen 2000, the Coconut Monkey games, Gun Battle (single-computer multiplayer only), Paragunner, Dopefish
Akuji the Demon (one hour long and really easy)
Lightbikes (less awesome Tron Lightcycles game)
Shooters Solitude
Miko-san's Miracle Board (3d platform/puzzle thing, okay, too long for no saving)
Mind Arms (shmup)
Magical Feeling 2 (puzzle)
XEvil (action, an older one I first played on Linux)
Magebane 2
Eternal Daughter (sidescroller)
Overgod (shmup)
Medicalat (shmup)
Cycles 3D (Tron Lightcycles game)
Burokuzu (Breakout-style
Atomic Butcher (unique sidescrolling platformer, somewhat foul language I think)
Castle Attack
DX-Ball 2 (Breakout-ish)
Mage Craft
Winged Gear (shmup)
Radio Zonde (shmup)
Stack Attack
Masashikun Hi (by the guy who made Gal Pani X and Sispri Gauntlet) (olympic sports-ish thing in japanese)

Windows Freeware, Not as good (most of these I just don't keep, but these are really small so I left them)
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Wirehang Redux
SideSwipe (one level)
Wok
BZFlag (multi-computer multiplayer only)


Games that were once retail games, but are now freeware downloads that I got the free versions of
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Red Baron
Betrayal at Krondor
Starsiege: Tribes
Anarchy Online (not worth the time)
Balance of Power 1990 Edition
Dink Smallwood
Castle of the Winds
The Ardennes Offensive 2
Ground Control
The Elder Scrolls: Arena
Zork 1-3
Caesar
Flight of the Amazon Queen (SCUMMVM)
Galactix (DOS version -- Windows is still shareware)
God of Thunder
Skyroads
Tyrian 2000
Jetpack 2.0
Squarez Deluxe
Beneath a Steel Sky (SCUMMVM)

Edit: sorting the list to put stuff by the same author together within each group and add some notes...