You will want a 16 ga. straight finish nailer. This will shoot nails from 3/4" to 2-1/2", which should handle most of your needs. Do you already have a compressor? Porter-Cable makes several different kits which include a compressor, nailer(s), hose, and all fittings you need. You will find that you will need more than one nailer. When installing casing around windows and doors, I use a brad nailer to attach the casing to the jamb, then I use the 16 ga. nailer to attach the casing to the wall. I have a 15 ga. angle nailer, but I seldom use it. If you already have the compressor, and just need the nailer, go with Porter-Cable or Senco. They are the best out there. Hope this helps.

http://www.amazon.com/Porter-CFFN251N-Nailer-Finish-Compressor/dp/B002JASUQA/ref=sr_1_10?ie=UTF8&s=hi&qid=1249043423&sr=1-10