Impact Wrench
Perhaps the most useful and effort saving air tool.  The impact wrench can be used almost anywhere it can fit.

Die Grinder
Need to take a little or a lot off, enter the super file.

Disc Sander / Grinder
Uses various disc types and grits, allows making quick work of your grinding/sanding needs.

Chisel
Aggressive tool used for cutting and shearing.

Reciprocating Saw
Small saw allows access to tight spots to make gentle cuts

Cut Off Tool
This tool can be used to cut fastners, pipe, and whatever else needs cutting.

Tire Chuck
The standard tool that goes with any air compressor.

Straight Line Sander
This sander is great for larger sanding jobs, allows you to maintain smooth straight lines.

Air Ratchet
Allows removal of nuts and bolts without requiring the side to side movement of a normal ratchet.  Makes a lot of cool noise too.

Blow Gun
Clean stuff off and make funny faces

Grease Gun
Handy tool that makes a grease job easier and cleaner.

Orbital Sander
Makes a nice smooth finish without swirls.

Drill
Air powered drills are usually smaller and lighter than their electric counter parts.  This is good in tight spots.

Nibbler
Useful cutting thin metal and plastic, allows for tight turns.

Butterfly Impact
Small job impact that fits in your palm, high speed for fast nut and bolt removal.

Air Compressor Components and Accessories
Filters, regulators, oilers.  Things that will keep your investment running for years.