Copy a file's full path

Select it and press ⌥⌘C. Paste the path anywhere.

How to do it

1. Select a file or folder.
2. Press ⌥⌘C (Edit ▸ Copy as Pathname).
3. Paste the full path anywhere: Terminal, a chat, a document.

Shortcuts

⌥⌘C

More detail in the guide: Keyboard shortcuts