Mac OS

# Fixing keyboard typing issues: e.g. while pressing ` print outs ±
sudo open /System/Library/CoreServices/KeyboardSetupAssistant.app/Contents/MacOS/KeyboardSetupAssistant

Source http://m10lmac.blogspot.com/2009/12/fixing-keyboard-type-problems.html

Reboot into recovery via terminal

sudo nvram "recovery-boot-mode=unused"
sudo reboot

# back to normal
nvram -d recovery-boot-mode