This Napoleon Built - In gas Fireplace is a little different from the rest of our list but we think it's the best direct vent gas fireplace we found. (geekwrapped.com)
What exactly is a direct vent gas fireplace? (geekwrapped.com)
The caldera of Tupan Patera, named after a Brazilian thunder god, reveals itself to be a strange and dangerous place, replete with hot black lava, warm red sulfur deposits likely deposited from vented gas, and hilly yellow terrain also high in sulfur. (apod.nasa.gov)