Just as everyone agrees that music is art and films/movies are massive works of art, I advocate a step further for games as simply being interactive films. There is a ton of thought that goes into these creations. When you see how the best game designers also painstakingly create real, developed characters with whose true sacrifices we can most certainly relate—and you for example realize just how massive and intricate the fantastic world of Studio Pixel’s Cave Story is (which is probably the greatest single game on this page)—you can’t not appreciate such incredible dedication and work. Here is a collection of the best freeware Windows games that I’ve ever played: true works of art indeed. (Red text marks games that are also Mac OS X-compatible.)

Regarding Japanese games: some of them may be difficult to access or even understand how to play; watch for telltale URLs (such as those that include the word “download”). Then check configuration executables for key mappings; nearly all Japanese games utilize the arrow keys with the keys Z, X, and C, or so.


Action/Adventure/Arcade
Battleship 88: Iron Hero: an isometric naval combat game
Beacon: a suspenseful side-scrolling platformer
Cave Story: a side-scrolling RPG platformer, created entirely by one man (programming, story, graphics, music, everything!)
hets: a side-scrolling arcade gunner

D. Ikushima, a.k.a. Metal Clover:
FrontLine: an endless side-scrolling infantry combat game
Navy Mission: a 3D naval combat simulator
Javel-ein, a smooth yet tricky side-scrolling platformer
Long Lance: a (Navy Mission-inspired?) 3D naval combat simulator
N: a side-scrolling platformer
Rumble Box (Wikipedia): a creative 3D beat-em-up
Shoot First, a roguelike shooter (also capable of local two-player)
Speedungeon: a frantic arcade game (note: it has no save file, so finish the whole game in one play)
Star Guard: a retro-style side-scrolling platform shooter
The Snowball Fighter: a Japanese hybrid third-person action-puzzler
Tsunami Cruiser: a classic survival arcade shooter
Browser (no download)
fl0w: an aquatic organism life simulator
HaxBall: a top-down exclusively online-multiplayer hybrid sports game
NEKOGAMES:
CURSOR*10 & Cursor*10 2nd Session: frantic, time-based puzzle games
Xana Neko & Xana Neko 2: side-view action-RPGs
People: a thoughtful portrayal of society and destiny
The Company of Myself: dark, abstract puzzler
Throw Out: the best Breakout clone in existence
Z-Type: an interactive typing test (my best: dying on Level 29 in Expert Mode!)
Casual
BUBBLEBURST: a silent top-down coffee-break game with wonky physics
Esc: a frantic coffee-break keyboard-mashing game
Knytt, Knytt Stories, and Within a Deep Forest: side-scrolling ambient explorers
Kumoon: a third-person puzzle shooter
Secret Exit:
Pogo Sticker, a side-scrolling rag-doll physics game
Stair Dismount & Truck Dismount: 3D rag-doll pain simulators
Sumotori Dreams (Demo): a 1- or 2-player 3D rag-doll wrestling simulator
Hotseat Multiplayer
In “hotseat,” all players participate on the same one computer.
0space: a retro-style futuristic infantry combat game for 2-4 people, inspired by a scene depicted in Orson Scott Card’s novel, Ender’s Game
Battle Painters: a Japanese top-down 1- to 4-player competitive family game
Building Panic: a cooperative 1- to 2-player Japanese side-view action game
Cephalopods Co-op Cottage Defence: a cooperative 2-player survival game
Cowboyana: a hilarious side-scrolling 2-player Wild West “simulator”
Eggnogg: a side-scrolling 2-player dueling game
Foiled!: a two-player game involving dueling for each other’s souls
Forget-Me-Not: a one-or-two-player game depicting Pac-Man as a hectic roguelike-like shooter
Liero (Wikipedia): a classic, highly customizable side-scrolling DOS-based deathmatch game for 1-2 players, portraying “Worms” in real time
Liquid War: a pixel-based multiplayer real-time strategy game
• Das Uberleben: skydiving gone horribly wrong
UFO Game: a 1- to 2-player UFO fighting game
Real-Time Strategy/Tactics
Attack of the Paper Zombies (direct local download): a futuristic infantry tactics game and Alex Vostrov’s free predecessor to his commercial Infested Planet
Drone: a top-down strategic defense command game
Ground Control: a 3D futuristic tactics game, released as freeware in 2007
Spatial: a simple yet challenging 3D space combat simulator
S.W.I.N.E. (Wikipedia): a humorous 3D military tactics game, released as freeware in 2005 by developer Stormregion
Warzone 2100 (Wikipedia) by Pumpkin Studios: an open-source 3D futuristic strategy game, released as freeware in 2005 by publisher Eidos Interactive
Turn-based Strategy/Tactics
Drain Storm (note): a DOS-based top-down roguelike
Sil: a tactical roguelike combining the stealthiness of Metal Gear Solid with the First Age of J.R.R. Tolkien‘s Middle-earth
Tower: a glitchy, 3D, OpenGL-powered roguelike
Shooter/Shoot-em-up
ABA Games (Wikipedia): a collection of 3D Japanese shoot-em-ups and shooters by Kenta Cho
Amanagi: a 3D Japanese side-scrolling shoot-em-up
Die Slave: a 3D Japanese side-scrolling shoot-em-up
GROBE-DA (local download): abstract, high score-based top-down shooter
GunViper: a 3D Japanese vertical-scrolling shoot-em-up
Innawoods: a single-player or multiplayer survival-horror FPS, initially made in 48 hours
Soldat (Wikipedia): a side-scrolling “shareware” infantry combat game
xSynergy Gate: a 3D Japanese vertical-scrolling shoot-em-up
Uncategorizable
An Occurrence at Owl Creek Bridge: a work of art grounded in American historical fiction
Bernband: a casual day in the life of a pff (alien)—a game with no objectives
Red Rogue: an insanely complex, detailed side-scrolling “roguelike-like”