List of Halo 5: Guardians commendations/Assist

Helping Hand
Earn any assist

Oddly Specific
Use a grenade to retrieve a power weapon for you or a teammate

Scrapyard
Assist in the destruction of a vehicle

Positive Contribution
Finish with KDA over 8 in any Slayer gametype in matchmaking

Now You See Me
Distract an opponent who is then killed

Passing Through
Drive a vehicle and have a passenger kill an opponent