[Jeff Higgins]

Are we talking a powder burning cartridge firearm or an air rifle? There is a big difference in range, effectiveness, legalities, and such.

If it's going to be an air rifle and you don't like the slow pace of the single shot springers and pumps, you can go pre-charged pneumatic. Many are repeaters. I would go bigger than .177, however - .22 does a much better job even on small rodents and such.

Rimfire .17's come in at least a couple of chamberings. The .17 HMR is in the performance range you seek, but it's like any firearm - can't use it in the city or other populated areas. There are both legal restrictions and safety considerations.

There are a number of .17 centerfires available as well. These are very, very specialized tools for the seasoned, dedicated rifleman / handloader. Some are capable of very high velocity (well in excess of 4,000 fps), but that comes with a price - rapid barrel wear. Ammo is horribly expensive, hard to find, and pretty limited - like I said, a bandleader's proposition.

Those are the three broad categories of .17's. In the end, the only one that makes sense within its category for varmint shooting is the .17 rimfire. Above and below that, in centerfires or air rifles, .22's make more sense.