(This answer pertains to air guns NOT airsoft that is a different question:)
All the brands make excellent, good and average air guns. One brand I would stay away from is Marksman. The quality is very poor. Expect to spend over $60 for an average airgun and over $100 for a good airgun. An excellent air gun will cost you well over $200. If you want to see a large selection of airguns online then see the "Pyramyd airgun link" below.
If you want a better understanding about the different types of airguns then read the bottom half of my profile "Air gunning" on the #2 link below.
Air Gun Category Supervisor.
The gun that it is modeled after is not that important. The main issue is who makes the gun you want to buy. If it is a really cheap brand you will probably get a gun that the trigger will fall off of in about a day, no matter what stile the gun is. If it is a nice brand though than you will get a nice gun that works reliably and its up to your taste as to whether you get the AK47 or the M4.
Brand to brand it varies. it can be anywhere from 250 fps to 500fps depending on the quality and brand.
Colt makes a 1911-A1 Pellet gun made by Umarex. I know of no BB gun unless you are asking about an Air Soft gun. The Pellet gun is very good. I can not answer about an Air soft gun.
yes
Nitro duck is a good brand, but tippmann is better in my opinion.
Craftsman is a good brand of air compressor, it has good hp rating, puts out sufficient scfm. Good warranty, and their products are made to last, as long as its used for that intended use.
It's perfectly fine to run the air conditioning, brand new or not.
200 TO 400
For an air soft gun it's average. Air soft guns can reach 400 FPS.
Tippmann is the best brand too get. Spyder is another good brand that isn't as good of a gun but Tippmann's are a bit more expensive but there is really no difficulty with Tippmanns at all. Invert mini is the most expensive gun around these days ( 500$ ) or the Bob Long guns.
Springfield (one word) has made very good guns for a long time.
Hi-Point makes substandard crap, mostly plastic, guns. Sorry, you get what you pay for.