I have a bunch of air rifles from pumps, springers and PCP's. I have Marauder rifles in 177, 22 and 25, a 22 Marauder pistol and a 22 Discovery. It is hard to go wrong with the Marauder line even though there are tons of other guns on the market now. If I could only have one, it would be the 22 rifle. Second choice would probably be the 22 pistol. I'd look around and see if you can find any refurbished deals. Airguns of Arizona used to have them all the time and you could save 30% or so off normal pricing and get a great gun.
The 22 rifle is pretty quiet out of the box. I can shoot in my backyard with neighbors out on either side.
Getting into PCP guns can get pretty expensive especially if you don't want to use a pump to fill. I have a couple manual pumps and also a scuba tank to refill. I planned to get an air compressor but really haven't been shooting near as much in the last few years.