Alt+F7 -> fulltext search, only in given file types, in archives (recursively), limiting for size, date, regexp etc. - way more powerful than any other tool I've ever used.
Viewing and editing files directly in archives (or in archives in archives in archives) without manually unpacking - as mainly java dev I do this very often. Again the speed and convenience is unmatched.
Very good built-in multi-rename tool, with preview of changes, GUI for this is so much better than any command line tool.
Very good file comparison tool - cleaner than anything other products (or dedicated ones) bring.
I don't want to end up listing all features of Total commander, but suffice to say its too my first tool to install (after firefox with ublock origin). Its not as much about how content I am using it, but whenever I see colleagues doing similar actions, they are maddeningly slow, ineffective and sometimes even give up for task that takes me few seconds. But that's full time usage of 2-pane mode since 1993, never saw any appeal in those simple explorer-like windows when I can be super quick with few shortcuts.
Other benefits are i like fast file editing, quickly exploring an archive or zip file and scheduled copy/move tasks.