An Air Compressor gives you the ability to travel with confidence in all terrains. For example: Beach driving requires lowering your tyres pressure to around 18 PSI. When you get back to the tarmac, you have to pump up your tyres or risk damage to the side walls from excessive heat build up.
Look for something that can output around 150PSI. This will get 4 tyres pumped up to your road pressure in around 15 minutes. Air compressors like winches can get hot ! So be careful when handling after use. Let them cool down before storing away. Find a permanent spot in your 4WD for storage and you'll be travelling with confidence. There are also onboard air compressors that can be used with the flick of a switch inside the car. They can also be used for Air Lockers and other benefits like using an air gun for blowing out Air Filters on dusty roads etc.
Prices can range from $150 to $800 depending on what you need. The dearest is not always the best, look for a name brand that has been reviewed and used extensively. The Air Compressor is every 4 wheel drivers friend, especially when you're a along way from the nearest service station.