Is there any way to completely disable the caps lock key without using any third-party apps?
(Virtually, of course—I don't plan on jamming something under the key.)
Just use the Keyboard pane of System Preferences.
Click "Modifier Keys", and set "Caps Lock" to "No Action".
In System Preferences, go to Keyboard > Keyboard > Modifier Keys… From the popup that appears, you can change caps lock's function to another modifier key, or to "No action."
The options available in the pop up menu: