I'm thinking of a feature where you can change your notification sounds (on Desktop) between the servers that you are a part of. Like let's say Server A has the original AIM sound effect*, and Server B has a sound effect from The Jetsons.
It's basically simple, and I'm sure this is a highly-requested feature among the Discord community.
*Sound effects could be changed via .mp3 files, .m4a files. etc., that you have on your computer.
EDIT: Also, would be nice to be able to have an AOL Instant Messenger-style feature where you hear a sound effect when you send a message. This sound effect should be completely optional and if you choose to enable the feature, it can be customized with the same method as aforementioned.