EarTrumpet - Volume Control for Windows
Volume2 - Volume2 is an advanced Windows audio mixer, a complete replacement for the standard Volume Control.
KMix - KMix is an application to allow you to change the volume of your sound card.
Sound Control - App-specific volume control
A-Volume Widget - A-Volume Widget is a floating volume control tool that allows users to use their hard volume keys along with the mouse.
SoundSource - The sound control that should be built into MacOS