Radial blur
A blur that smears every pixel toward or away from a centre point so the image seems to stream out in shafts of light — the PC demo seasoning of choice around the turn of the millennium.
The technique samples the image several times along the line between a pixel and a centre and averages the result. A cheaper trick was to redraw the previous frame slightly enlarged and blend the new one over it, giving the same smear over time — the video feedback principle. With bright objects against a dark background it reads as volumetric light, god rays, years before game engines did it properly.
In the late 90s it ran in software on the CPU and ate a large slice of the frame budget. Programmable GPUs turned it into a few lines of shader code, and from there it became so common it turned into a cliché — sceners still joke about demos using it to dress up simple 3D scenes.