This is Gonna Hurt - 2500 XP
Complete any Campaign Mission on Heroic or higher difficulty with the Famine, Tilt and Thunderstorm skulls.

Requiem Rumble - 6117 XP
Complete Requiem on Legendary difficulty with the Mythic, Tilt, Tough Luck and Thunderstorm skulls.

Spartan Ops

Creeping 'n Crawling - 1250 XP
Kill 80 Crawlers.

Watchful Avenger - 1500 XP
Kill 20 Watchers.

Knightmare - 1750 XP
Kill 30 Knights.

War Games

Spray and Pray - 4200 XP
Get 80 kills with an Automatic Loadout Weapon.

The Kill-o-Tron - 6200 XP
Earn 12 Multikill medals in a single match.

Click here to see a complete list of this week's Weekly Challenges.