Hold-and-Modify (HAM)
The Amiga's cheat mode that showed all 4096 colours at once by letting each pixel tweak just one colour component of its neighbour.
HAM (Hold-and-Modify) was a display mode in the Amiga's OCS chipset from 1985. Normally the palette ran to 32 or 64 colours, but in HAM a pixel could instead "hold" the previous pixel's colour and modify one of its RGB components. That put all 4096 colours on screen at once — something no contemporary home computer could manage.
The price was artefacts: because a colour was built up stepwise from the neighbour to the left, sharp edges left small colour fringes. Even so, HAM made the Amiga the king of image display in the 1980s, and the later AGA chipset lifted the trick to 262,000 colours in HAM8.