Halo 2 > Halo 3 > Halo 3 ODST > Halo Reach > Halo CE
Based on campaigns.
Do I kill you or what? 10g-On Gravemind, kill a brute, jackal or drone to save a grunt, hunter or elite with very low health
Taste of your own medicine 50g-Kill 100 covenant with covenant weapons
Jealous of your car 10g-Destroy all the civilian vehicles still intact on the mission Metropolis.