Ever wanted to find out all the keyboard shortcuts for an app but can never be bothered to dig through the settings to find them? Well CheatSheet is easily one of the best apps ever on the Mac App Store.
CheatSheet is one of the most useful apps I've ever used. What CheatSheet does is let you find out all the shortcuts available to you in an app by simply holding down the cmd key.
So when in Photoshop you can hold down the cmd key (for how long you hold it down for can be adjusted) and an overlay will come up showing you all the keyboard shortcuts available to you right now. Once you let go of cmd key it'll then just disappear.
It's so bloody useful and amazingly it's completely free so download it now!