OutRun 2006 (flame rings in 4th level on the left, 4 morph weights IIRC)
Depth buffer reads from the CPU
Midnight Club: LA (sun lens flare)
Syphon Filter (light halos (lots per frame!))
WipEout (sun lens flare). Multiple reads per frame to get an average.
a few more
Direct color buffer reads from the CPU
Coded Arms: Contagion (reads a single pixel from the alpha/stencil channel to identify enemies to lock-on)
Dangan Ronpa, Dangan Ronpa 2 (renders a separate mini buffer to select clues, people)
Motorstorm (light adaptation)
a few more
Color buffer format aliasing
Cars Race-o-rama
OutRun 2
Split/Second
Spongebob
Depth buffer manual swizzling through geometry
This is a mistake that a few games have made - the PSP has hardware to swizzle depth buffers to linear, but instead they use triangles. This applies to the particle effects in these games