Pretty much every planet in the Star Wars Universe. All of them seem to be "one climate planets." There's the "ice planet" the "desert planet" the "volcano planet" the "city planet."
And while it could be argued that the volcano planet was a proto planet, planets like Hoth and Tatooine make little sense in the grand scale of things as they're both "single enviroment" planets. Consider how Earth has a wide range of enviroments across its surface, having a planet that's just a desert planet-wide is a little silly.
There
is a planet that's just a desert planetwide. It's called Mars. A desert is an environment with little or no water, and it's certainly possible for an entire planet to be nearly devoid of water. (Okay, Mars has plenty of water, but it's frozen.) In fact, when Earth formed, all its surface water evaporated into space from the heat of the molten planet. Once it cooled, its volatiles were replenished mainly from cometary infall. In a system with less cometary ice available -- say, a binary system where the combined heat and stellar wind of the two stars had stripped most of the volatiles from the protoplanetary disk -- a planet could easily end up quite arid planetwide. And wouldn't you know it -- Tattooine has two suns!
As for a planet that's completely covered in ice,
Earth may have been like that once too, hundreds of millions of years ago. There are certainly plenty of moons in the Solar System, around the four giant planets, that are made largely or primarily of ice. Galaxywide, water is far more commonly found in the form of ice than as a liquid or gas.
And an entire planet dominated by vulcanism isn't implausible either. Again, Earth went through such a stage, and Jupiter's moon Io is currently in one.
The case that's really implausible, though, is a city planet. An entire world that's nothing but city? How could it function? Where's the oxygen and food coming from? Even if those were artificially supplied, a planetwide city would roast itself. Cities are massive sources of heat, so massive that they alter the climate around them. An entire planet covered entirely in city, with the population density of a city, would generate enormous amounts of heat with nowhere for it to go.
Although there is one way it could work, as suggested by Larry Niven and Edward M. Lerner in their Known Space novels
Fleet of Worlds and
Juggler of Worlds. A planet like that, totally covered in populated urban environment, could function if it were either on the far outskirts of a star system or (going back to the start of the thread) traveling in deep space as a rogue. Its technology and population would generate so much heat that they wouldn't need a sun, and in fact would need a total absence of stellar heating. Given that, perhaps the one truly implausible thing about Coruscant and Trantor is that they have suns.