Useful audio effects that are applied to all system sounds
Is that one video too quiet and you need the volume boosted? Or do you want to add some echo to your favorite music, or are your speakers set up backwards and you need to swap the left and right outputs?
With EasyEffects you can do that.

I (Botspot) have been using this for several months now and find it quite useful.
With a big sound system, the room would shake whenever a YouTube video had some low wind noise, and EasyEffects fixed that with the "Equalizer" plugin where low frequency sounds could be limited.
Also check out the "Autogain" plugin. It turns down the volume during loud portions and raises it when someone is talking quietly. Perfect for class recordings where the teacher always talks very quietly, but occasionally shouts or pounds on the desk, and you don't want to wake up the neighborhood.
There are 24 effects in total, each with many presets and parameters to fiddle with. Also, effects can be applied to system input sounds (microphones), so you could improve how your voice sounds for audio recordings and voice calls.

To run: Menu -> Sound & Video -> Easy Effects
To run in a terminal: easyeffects
