I was messing with the Android lock screen earlier, and in the process I changed my lock screen from my old pattern to a new PIN, and I managed to forget it straight after I have locked the screen.
Cue five minutes of panic, ten minutes of pointless brute forcing back into the phone with no luck.
However I have found a solution!
If you have your Android device enrolled with Android Device Manager, you can go to the following page (https://www.google.com/android/devicemanager?u=0), and all you need to do is to LOCK the device, which will then give you an option to set a new PIN, voilà!
Granted, the device will need to be connected to the internet (WiFi or cellular) for this trick to work, and if it's not showing up in ADM, well, better luck next time!