I have a ChannelMaster . Mounted with a rotor and an external signal amplifier, it works great at pulling in HDTV signals from towers up to 50 miles away.
People have also had much success with Radio Shack antennae. I've heard second-hand recommendations against Terk.
I have the Square Shooter and it works great for me. About the size of a pizza box, so it is very easy to mount with the supplied mounting bolts. Get very good signal strength for my location.
I would check out some of the UHF antennas out there before buying a Square Shooter. Look at the Channel Master 4221A 4 Bay model or the 8 bay CM 4228A if you are trying to pull in distant signals. You can find them for good prices at warrenelectronics.com. They also have great prices on preamps (like the CM 7777) and rotors if you think you will need those as well.
PS - they also have the Square Shooter for sale at Warrens ($89 for nonamplified and $110 for the amplified version). But a CM 4221A 4 Bay antenna and preamp (CM7777) is a better solution IMHO and will cost about the same as the unamplified Square Shooter.