Lunar.fyi - Control monitor brightness, adapt using the ambient light sensor, adjust volume, switch inputs and turn off displays without fiddling with clunky buttons.
Sound Control - App-specific volume control
DisplayBuddy - Control the real brightness of your monitors directly from your Mac - no need to touch the buttons on your Monitor.
EarTrumpet - Volume Control for Windows
Nocturnal - Have more control over your screen at night 🌙
Background Music - Control the audio on your Mac apps from the menu bar