AFLI
A C64 graphics mode that pushes colour resolution to 8×1 pixels in high-resolution monochrome mode — at the cost of nearly all the CPU.
The FLI trick forces a bad line on every raster row so the VIC-II reloads colour memory 25 times more often than normal. AFLI — advanced FLI — does the same in high-resolution bitmap mode, yielding 320×200 with its own colour per 8×1 cell instead of the usual 8×8. The result comes close to free colour per pixel row, something the C64 was never meant to manage.
The cost is steep: almost the whole processor goes to feeding the VIC-II, memory use is high, and the technique leaves a characteristic unusable strip on the far left where bad-line timing eats the first pixels. NUFLI and other late variants refined the idea further.