clicking with the mouse button will enable/fire most items that are in the highlighted quickbar slot.
At least the following actions are executed despite open chat:
- Firing missiles
 - Activating any effect computer
 - Open advanced build mode (der_scheme has bound this to 'F')
 - Open/close chat (SpaceKing bound his chat key to a letter)
 - Record GIF (is this a good or bad thing?)
 - Activating cloaker/radar jammer