The GCODE I use a lot

GCODE Description Example
G91 set relative mode  
G90 set absolute mode  
G92 set position G92 E0
G0 move axis to position G0 F200 E20
M500 save parameters to eeprom  
M503 report in-use eeprom parameters  
M302 S0 enable cold extrusion  
M119 endstop states  
M120 enable endstops  
M121 disable endstops  
M122 TMC Stepper debug info  
G34 synchronize z axis motors  
G28 home all  
G29 level bed  
M600 filament change  
M603 configure filament change load/unload length M603 L1000 U1050
M701 load filament  
M702 unload filament