If you're on a pvp server and the person you're raiding has a giga, if you can, focus fire on it...it will eventually enrage and attack all its friendly dinos and structures around it
These things (when tamed) take HUGE fall damage. Though if you are falling on it and have time, quickly press the dismount button. The dino will take 0 damage from the fall, you might die from the fall but giga will be fine. (Works on any dino)