Okay, I've been playing for a very long time now, and still have never made a character with points spent in the Listen skill. The recent improvement to spotting hidden mobs is a help, but still not entirely worth the points. I mean, what's the difference between listen and spot then?
This idea is to use the listen skill in conjunction with your mini-map. While the mini-map currently has waypoints and party members shown, it could be used to show enemies for players with high listen skills. In sensical terms, a character could hear an enemy approaching from behind, coming around a corner in the environment's hallways, or even through doors (a highly skilled listener can put his/her ear to the door and decipher the number of mobs on the other side and their approximate locations- depending on how skilled the character is).
This could be a very simple development by using flashing, red icons on the mini-map which give the approximate locations of these mobs. It's already coded with party members- ergo it shouldn't require written code from scratch- and would give many players an extremely important reason (especially rogues) to invest in this skill. More importantly, it would most definitey give players a new tool to play with and add some new twists to gaming styles.
This would also open up some new clairvoyant arcane spell options.
That's the 2cp version.