I just bought this one: I was amazed at the quality of it for the price. I bought it for taking good pictures of the moon (I am a moonatic)
I have a lot of lenses, the best are the Canon AF in a few ranges, they have so many lenses, it's silly. My favorite for a general purpose lens is an 18 to 135 MM and shooting at 18 MP.
With that lens, you can get most images in a hurry, even birds within 50 yards and still have a usable image. If you get a 75 to 300 AF, it's great for fast moving stuff and athletics but you cant take a close up image.
Fun lenses are fish eyes but they have such a limited purpose it's better to just buy a $40.00 fish eye adapter. It's not as crisp as it would be with an actual fish eye but software can correct most of that if you get an initial crisp image....in fact any Canon AF lens is worth the price but they cost a lot of money.
This lens below can also be 2X'd. It has to be stabilized to get a clear image but the reality is - it is more of a telescope that attaches to a camera as opposed to a photographic lens. I''m really happy with it.