Bill Maher. You think Letterman is smug? Try Bill "Believers are all a bunch of idiots" Maher.
Richy Gervais. IS pretty obnoxious. Intolerant Atheist like Maher.
Ellen DeGeneres. Simply not funny.
Chelsea Handler. CAN be funny at times, but she's WAY overdone the "I'm a drunk slut and proud of it" schtick she does.
Lisa Lampanelli. They don't call her the "Queen Of Mean" for nothing.
Dane Cook. WAY overrated. Only occassionally funny.
Dennis Miller. Not funny anymore. More of a political commentator now.
David Letterman. Like others have said---smug---also can be very mean.
Wanda Sykes. Mostly "I'm Lesbian, a Democrat, an Obama supporter and everybody who disagrees with me is a homophobe and an idiot" material.
Sinbad. We've heard the "all kids are brats and you should beat the **** out of them" message one too many times.
Patton Oswalt. Unfunny.
Chris Rock. Not funny anymore.
Rosie O'Donnell. Never found her funny. Hated her on The View.
Those are some off the top of my head.
Hope that "helps."
Actually---personally, I feel a good portion of today's comedians are just not funny.
MY opinion, of course.