TUMIKI Fighters (Windows)

Kenta Cho's quintessential STG masterpiece and early example of a stunning independent production distributed freely online, Tumiki Fighters is a side-scrolling arcade shooter composed entirely of toy blocks, where you can attach any fallen enemy to your own ship—increasing your resistance and firepower but also greatly enlarging your hitbox, which also increases the chances of being hit. This turns the game into not just a shooter but also a management simulator of sorts, in which you must decide which enemies to attach to your ship and which might be better avoided. It's surprisingly more challenging than it looks.

On an added note, this title has spawned its own fan creations, including Touhou-inspired ones.