Bryan Cranston is an avid speedo lover.
One of his King of Queens appearances was centered around this fact when he invited Doug and the guys (but not Carrie) over to his pool. I want to say s2, "Swim Neighbors"?
I want to say he also sported a pair in "Seeing Other People"? w/ Jay Mohr and Andy Richter.
His character was married to Jay's fiancee's sister and he hit on her while wearing them.
btw, Andy wore a 'flesh speedo' for those occasional 'nude' sketches on Conan O'Brien, like the "Turkish Bath" that turned out to be the Today show set with Matt Lauer. There are a couple of non-pixelated pics floating around out there. they hid NOTHING, so it's a good thing he's blond, unfortunately.
Other than that, only David Duchovny's little red speedo on X-Files (s1 or 2?) and
Nicholas Brendan's on Buffy (HS swim team ep) are the only other to come to mind.