As of 6:40 PM of the 14th April (Australian Time) I have plugged my Xbox One Controller in and launched Halo.

NOTE: I have the Logitech G300s Gaming mouse software installed and programmed the mouse to do specific actions in FPS and MOBA games.

The procedure was as followed:
1. Launch Halo while Xbox One Contoller is plugged in.
2. The game will only recognise the controller instead of keyboard when plugged in.
3. As no controls are programmed/re-programmed, the Xbox One can't interact with menu stuff unless unplugged so it would return to normal Mouse + Keyboard Interaction.
4. Checked the Gamepads settings and Saw a duplicate profile of the Xbox One controller for Windows. (So there's 2 of the exact kind)
5. Restarted Halo with contoller plugged in and saw only one Xbox One controller profile.
6. Unplugged controller while Halo is still running and returns the control to mouse + keyboard.
7. Go to controls and assigns controls for Xbox One Controller.
8. Clicks on the command and plugs controller in to press a specific button for each action.
9. Step 8 repeats.
10. Saved settings for controller.
11. Enters any map.
12. Halo only returns control to the Xbox One controller without Mouse + Keyboard so no way to press the ESC without unplugging controller.
13. Unplug the controller before hitting ESC to bring the menu.

I think the Xbox One Controller is conflicting with my Logitech G300S Gaming Mouse software and its programmed side-buttons.

Any suggestions are welcome.

Use Xpadder for binding the pause key to the ESC button.

The controller can use menu_select and menu_back on the buttons by default if you assign them. I don't have any suggestions for the software conflict though, sorry.