I got into airguns a pretty good bit a few years back. Pretty crazy how mush stuff is out there right not. The good thing is that there is a ton of info and resources available.

If you intend to hunt with it theres two main choices. You have springers (which will usually include the piston guns) like what have been mentioned here and then there's what is reffered to as "the dark side". That's PCP airguns. If you go the PCP route you will see some next level airgun technology. It's hard to ignore PCP once you know about it. I took the bait and ended up way deeper into airguns that I imagined when I first started looking.
Springer airguns have come a long way as well. You have people killing hogs and mid sized varmints with those things.

Gatewaytoairguns.com is a really good resource.

I havent really spent any time in the last 5 or 6 years looking at much airgun stuff but my little bit of research has lead me to an air rfile called the Seneca Aspen. That will likely be my purchase when I get back into airguns. It's not cheap but after I learned to look at airguns along the same lines as firearms I opened myself up to a really good experience.

My last air rifle was a used Bejamin Discovery that I modified and tuned. Just slightly less powerful than a 22 short out of a rifle. I was hitting marbles at 25-30 yards and they would explode into clouds of dust. I shot that thing more than anything else I've owned.

Good luck...