I was on Windows for a long time and switched to Mac about year ago.
Some things still looks strange and confuses me:

1. How to remove a file without mouse in Finder?
2. How to move (cut) a file without mouse in Finder? (`Ctrl`+`X`, `Ctrl`+`V` in Windows)
3. How to get common info about several selected files (for example their size)?
4. How to go back to previous folder in Finder without mouse? (`Backspace` in windows)
5. How to open one image and be able to move between pictures with keyboard (without another picture viewer software)?