Building on a previous comment regarding columns:
A feature I have used a lot in another editor uses the right mouse button and mouse movement to select a rectangular column over any number of characters and any number of lines. You can then use cut/delete/paste in the normal way, and the entire column is cut/deleted/pasted etc.
Really useful for tabulated data, the bane of my existence.
This is possible in Crimson Editor if you press Alt+C or click the toolbar button to toggle column mode. However, the right-click and drag technique to do it is a new idea to me.
Another useful feature: If nothing is selected on a line, pressing the delete key deletes the entire line where the cursor happens to be.
This sounds like very nonstandard behavior as the delete key generally deletes the character after the cursor. In Crimson Editor, if nothing is selected, pressing Ctrl+X to cut deletes the entire line and puts it on the clipboard.