OT: Today, the obvious contenders are Bloom Lighting and excessive Particle Effects (courtesy of Pixel Shader 2, of course). They are quite noticeable when the standard color palette for your average environment is in the darker spectrum.
The resulting contrast might look epic initially (as Gears of War 2 shows), but it gets real old, really, REALLY fast. For examples of excessive/inappropriate use of Bloom Lighting in particular, I cite Mass Effect 2.
Seriously. Half of the game, it looks like there's a divine glow coming from an unknown light source. Light just does not behave that way, no matter how pretty it looks.
The worst offender of all time is actually a game I otherwise adore: Shadow Complex.
It's based on the U3 engine, and so they just HAD to exploit the shit out of it; technically speaking.
Every opening corridor, every water texture, every semi-metallic/high-tech device has this Bloom-Effect on it and it's really distracting. I recall the hallway containing the last (and optional) suit upgrade. It's very white, and oddly lit.
I hadn't seen the color white being violated so strangely since I saw I-Robot.
Generic Gamer said:
The only effect that's ever struck me as excessive was the shine in Halo CE. Seriously, everything Covenant looked wet.
That's called Specular Textures+Lighting, and it's the one technical marvel that put Halo: CE on the map. Seriously, Halo probably would not have sold nearly as well if it weren't for that bit of tech, because I've seen what Halo: CE looks like without that (on PC).
It looks like total shit without it, to the point where it actually changes how the game's style looks entirely.