Air Pig
An air pig is essentially a small horizontal air receiver with a number of outlets on either side. It can be used as a local distribution point to supply a number of tools (for example).
The advantage of an air pig is that it provides a local store of air and acts as a collecting point for condensate which can be drained out before getting to the air tools and causing damage.
Often used with mobile compressors where the compressor is parked some way from the job and a long hose has to be used to get to the point of use.