Favorite supporting element

[ajb1978]

Shower thought here.  What are some of your favorite non-critical, non-essential elements of games you've played in the past?  Can be TLD, or anything really.

For me the thing that inspired this question was thinking about an old PS2 game RTX Red Rock.  The game itself was rushed to production resulting in a buggy, borderline unplayable mess, but one part really stood out as awesome.  The background music was composed of two tracks: the percussion, and synthesizer.  When not in combat, the syntheser track would play constantly, giving it a kind of unsettling, desolate atmosphere (which is appropriate since it takes place on a ruined mars base).  But when you started moving, the percussion track would also play, making it really feel like the music was perfectly in tune with your actions.  The end result was that it came off less as background music, and more like a movie soundtrack that was perfectly paced with whatever was going on.