This is the gun that Soviet cosmonauts took with them into space until 2006. From Neatorama:
Specifically, they carried the TP-82, pictured above. It had three barrels, the top two which fired approximately 40 gauge shotgun rounds. The lower barrel was chambered for the 5.45×39mm rifle round.
Why did the cosmonauts carry this gun? It wasn’t to fight off aliens, but protect themselves from human threats if they landed in unfriendly territory at the end of their missions.
If that wasn’t enough, the TP-82 also had a handy machete built into the handle.
More info here.