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For NES, another cool approach takes advantage of the fact that the cartridge is natively split between CPU memory and PPU memory. This means that it's possible to make a cartridge with RAM instead of ROM for the tile pattern data ("CHR" in NES jargon), thus enabling things like pseudo-framebuffer operation, compressed/generated graphics, and animations that work by modifying the tile data or depend on its organization in memory [1]. Strictly speaking, there's no reason that RAM and ROM couldn't be combined in this address space with a mapper, but I haven't heard of any cartridges that do so.

[1] https://wiki.nesdev.com/w/index.php/CHR_ROM_vs._CHR_RAM