Pluto
Pluto reaches somewhere between magnitude 13.8 and 14.1 at opposition making it a rather challenging object to see from washed-out skies. But Pluto’s tiny size helps us pull it out of the light pollution: because it is star-like, we can use high magnification to improve the contrast. Even from my light polluted front yard, I’ve seen stars of this magnitude with my 10 inch Dob using moderate to high magnification (150x to 250x). So in theory, Pluto is within reach.
Unfortunately, Pluto is currently located in Sagittarius. This is not good. That puts Pluto low on the horizon (and I have a particularly cluttered southern horizon). It also brings Pluto into view during the hazy months of summer, when transparency in the Washington DC area is consistently poor. Even worse, it puts Pluto right in the middle of the Milky Way, with lots of other stars of similar brightness. if you think finding a needle in a haystack is hard, try hunting for a particular 14th magnitude star in the middle of the Milky Way....
I’m going to try again this summer to see Pluto. I encourage you to try, too. Let me know if you succeed. The best way to be sure you have the right object is to observe it again a week or two later and look for movement. At moderate to high magnification the motion should be fairly clear. And let me know if you succeed!
Here are a few resources to help you in the hunt for Pluto:
Sky & Telescope Pluto Locator Charts for 2010 (you may need to register with Sky & Telescope to access this, but registration is free)
By the way, while Pluto has been officially demoted from planetary status, the Washed-out Astronomer will continue to treat Pluto as a planet, at least as far as this web site is concerned.