Lunar.fyi - Control monitor brightness, adapt using the ambient light sensor, adjust volume, switch inputs and turn off displays without fiddling with clunky buttons.
Paper by WeTransfer - A collection of creative prompts
Duet Display - With Duet Display, you can transform your iPhone or iPad into a second display to expand the screen space of your PC or Mac system.
Milanote - Milanote is a note taking app for creative work.
DisplayBuddy - Control the real brightness of your monitors directly from your Mac - no need to touch the buttons on your Monitor.
Astropad - Astropad is a free form drawing tool designed from the ground up to take advantages of the features offered by an iPad.