Killing Floor

Killing Floor is about a large group of sassy British people killing evil not-zombie mutants in order to gain a lot of DOSH.

Killing Floor Mod resources
ALL of the models from back when Killing Floor was an 'Unreal Tournament 2004 mod are in the game's files, including old, unused models that can be found in the mod version. These can be placed in custom levels as background props. Some of these are actually used in-game, such as the box of rockets behind the Merchant in certain levels and the hand grenade's model.

Red Orchestra leftovers
Killing Floor has several leftover models and textures from Red Orchestra: Ostfront 41-45. This isn't surprising, as the KF engine is based on the Red Orchestra version of the Unreal Engine 2.5 and is made by the same people behind RO. Like the Killing Floor mod models, the RO models can be placed in custom levels as background props.

Pinball Models
Models for parts of a pinball machine can be found in “GKStaticMeshes.usx”. None of them have their own textures; they all use the default texture. These models are too detailed and large to be a part of a prop. They could be props from a scrapped level based on a pinball machine, which would explain their size.