Just off the top of my head: cheap glow effect, ripple effect (e.g. when a bomb goes off), post-processing filters for things like film effects, etc. You don't

Just off the top of my head: cheap glow effect, ripple effect (e.g. when a bomb goes off), post-processing filters for things like film effects, etc. You don't need to be doing 3d work to make great use of shaders.