Depends on how wide you want to go and what kind of camera body you use. I've used a Canon 28/2.8 on a T2i body and even that seems wide enough for me, but would not be for most people. The lens is good, a bit of barrel distortion, but few wide angles don't have that, and it's correctable in processing. If you want wider, there's a 24/2.8 that is supposed to be pretty good, and then it starts to get really expensive.
Nice to see people recommending all of these lenses and have no idea what body the OP has and what he wants to shoot. What is wide angle? I consider 35mm pretty wide. There is also the term ULTRA wide angle. Who knows what the OP really meant.
Thanks everyone. I appreciate your time commenting. I have a canon eos 600D. I got a kit lens 18-55 EF IS II. Then tried the prime lens canon nifty fifty 50mm F/1.8 and i love it. My intetest are portraits and street photography and a little of landscape. That's why i would want to try a wide angle lens. Again, thank you.