Gravity hammer
From Halopedia, the Halo wiki
The Gravity Hammer (known as the Fist of Rukt[1]) is the personal weapon of the Brute Chieftain, Tartarus, and he alone can wield the mighty hammer. At 2.682m[2] it not only serves as an excellent melee weapon, but can alter gravity to move objects and living beings around.
It may contain shards from the mysterious crystal found in the book Halo: First Strike, as the crystal could alter gravity.
Trivia
Tartarus's battle hammer is named the Fist of Rukt. It is unknown what "Rukt" actually is or was. Presumably it is named after some entity, possibly the first to possess the hammer. It also translates to "jerks" or "tears" (as in the verbs) in Dutch, and "blood" in Sanskrit and Hindi.
In "Starry Night'"
In the "Starry Night" TV spot released on December 4, 2006, one of the Brutes that the Master Chief attacks is carrying a hammer. However, this is probably not the Fist of Rukt, and it remains to be seen whether or not it is even a gravity hammer.
