Bostitch F21 (haven't needed to change the tip and shoot hanger nails -- tool less operation though).
Bostitch/Porter Cable/Dewalt all parts of Stanley-Black & Decker. Not sure how interchangeable.
Paslode & Duofast are part of ITW.
I had a Duofast I bought at a pawn shop. It was worn enough that the nose was worn pretty smooth and couldn't tell the model #. But it would shoot round head nails (took it to a local supplier/repair chain) and bought round head nails. Probably should have tested it with clipped, as I suspect it would not have jammed near as often (I was invested in nails). And should have thought more about the worn out nose. Gave it away and bought the F21. I don't think it allows for a tool less method of clearing a jam (missed that detail), but have had so few jams that I don't recall them.
Watch out for sales on the specialty nails when you get the gun: ring, galvanized, stainless, etc. These are used for different purposes, but fence pickets, pressure treated, redwood, etc.
If it gets cold where you are at, get a squeeze bottle of below freezing oil, and regular temp oil. You can get a swivel hose fitting for the gun. Comfortable safety glasses, ear plugs are a must. Some guns allow you to direct the exhaust air, some don't.
Bought a 15 ga Senco finish nailer. No oil (yeah). A little large for finish work (usually 16 ga) as it requires more filler, and is probably a bit large.
Bostitch SB2-in-1 18 ga brad/stapler combo (narrow crown). Works well, occasionally wish I had a wider staple, but not worth buying another one and all the fasteners.
Grex 23 ga pin nailer -- great for not having to fill in nail holes!