IF you feel the need I guess a barrel, although my stock barrel out shoots both of my friends stock phantoms.
Durable like a tank
really cheap for the quality
hard to find upgrades(don't really need them too much though)
This is a great gun pump gun for any experience level. You wont have to worry about damaging the gun at all. The stock barrel must be some type of fluke because its more accurate than my 14" J&J ceramic on my 98c and the stock barrels on both of my friends phantoms for half the price. The gun has been discontinued now, so if you want to buy one you have to go to ebay, the trading forum or find the few new ones left in stores. This is a great gun to buy and if you have to loan it out, like all tippmanns, you don't have to worry about it, but the gun is pretty much indestructible seeing as how it appears to be cast iron. Auto-trigger is the most worthless feature in my opinion, simply due to the fact that it is a pump, because as you pump the gun to shoot fast you are throwing the barrel and your accuracy all over the place.
If you haven't played pump before I would recommend you try it, it is much more challenging and interesting. I would recommend this gun to both new and experienced pump players alike. It will last you for a long time to come and will support you well.