Step Forward and Step Backward – Multiple undos.
Fade – Not happy with the results of a filter or an adjustment? Choose this immediately after running the filter. By the way, did I mention this adds blending modes to all filters? Your filter collection just grew 2100%. Try it now! Give your filters new life! Remember: you must choose this immediately after running a filter. This is quite possibly Photoshop’s most underused feature. (Shift+Cmd+F/Shift+Ctrl+F)
Copy Merged – Copy multiple layers into one layer on your clipboard. Why flatten unnecessarily? (Shift+Cmd+C/Shift+Ctrl+C)
Check Spelling & Find and Replace Text – Because spelling errors are generally nonbillable.
Free Transform – This tool does it all. Access every layer transformation by Ctrl+clicking (right-clicking) while in free transform mode. Cut downs on image degradation by applying all your sizing, warping, and perspective changes at once. Cmd+T (Ctrl+T)
Purge – Free up space by deleting undos, clipboards, history! This will enable you to save and close when you get the dreaded “Scratch Disks Are Full” message.