For a good investment in a Break-barrel Spring Piston, the RWS 34. German quality rifle. In the Airgun forums I've been through, many seem to prefer the .22 caliber pellet version for hunting purposes, though a .177 caliber version can be quite capable too. Among the Beeman line (once known for their Quality Airguns) always look to the German-made R-Series. Most of the rest are of Chinese manufacture now.
The Gamo's biggest weakness, from what I hear is customer service and a trigger that many complain about, and there is a replacement trigger available that greatly improves the Gamo, and the various Chinese copies of. I have a Shadow 1000 .177 myself.
Then there are the Pre-charged Pneumatic airguns, where Crosman has made major inroads the last few years with the Discovery and Marauder.
A lot of it depends on how much you want to spend, and what you can handle. Break-barrels and under-levers tend to be long air rifles, a pump-up pneumatic is shorter and handier, and the PCPs are somewhere inbetween.