OBS Studio - Free and open source software for video recording and live streaming for Mac, Windows and Linux.
MSI Afterburner - Tool to manage video cards. Shows video card stats (temp, GPU usage, etc.).
MWSnap - MWSnap is basically a free to use Windows snapping tools that are used for snapping any part of the screen that is currently displaying on the front of all opened programs and windows.
ASUS GPU Tweak - ASUS GPU Tweak fully implements TechPowerUp’s GPU-Z analysis and monitoring features.
Greenshot - Greenshot is a free and open source screenshot tool that allows annotation and highlighting using the built-in image editor.
Guru3D - Guru of 3D: PC Hardware Reviews and tests