Okay...since nobody else has done it yet, I'll make the case for my home state:
California (and I'm not putting other states down, I've visited many of them, and liked them all, but California is my home).
The Sierra Nevada:
One of the most impressive mountain ranges in the country, it's also home to the highest point in the lower 48 states, Mount Whitney. What's really striking about the Sierra is just how fast they rise on their eastern edge. The floor of Owens Valley (the deepest in the country) is roughly 4,000 feet, and Mount Whitney stands at 14,505 feet. That's nearly 2 miles of elevation gain in only a couple of miles of horizontal distance.
The Sierra Escarpment:
The other side of Owen's Valley is bounded by the White Mountains (also in California), who's highpoint is 14,252 foot White Mountain Peak. Twice a year, gates near the mountain's summit are opened and you can drive a jeep trail all the way to the top, making it one of the highest roads in the country. To my knowledge, it is the highest mountain in the United States to have been summited via unicycle.
The Sierras feature other scenic destinations such as Lake Tahoe, the second deepest lake in the United States, and Yosemite Valley, the first land ever nationally set aside for public use (before Yellowstone even).
Tahoe:
Yosemite (hey, more Ansel Adams):
The Sierras are also home to the some stunning water features, including but not limited to Yosemite falls. At 2,425 feet, it is the sixth highest waterfall in the world, the highest waterfall in North America, and taller than the absolute highest point in 17 states.
Yosemite Falls:
The Cascades:
While the Cascades only briefly dip into Northern California, they certainly leave their mark. Medicine Lake Volcano is the most voluminous of all Cascade Volcanoes, and Mount Shasta is the most voluminous stratovolcano (the pointy ones that erupt in the most violent fashion). Mount Shasta also happens to be the second highest mountain in the Cascades, and is the second most active (after Mt. St. Helens). The large satellite cone on Shasta, known as Shastina, has enough prominence to be considered a separate peak under most mountaineering standards, but is generally not regarded as such. If it were its own mountain, at 12,330 feet, it would be the third highest in the Cascades, taller than the highest point in Oregon, Mt. Hood (which stands 11,249 feet). Because of its tremendous size and very active history, Shasta is considered one of the most dangerous volcanoes in the country.
Mt. Shasta:
http://img5.travelblog.org/Photos/13426/205919/f/1545860-Mt-Shasta-4312-meters-0.jpg (broken link)
Besides Shasta, the Cascades in California also feature Lassen Peak (10,462 feet), the only volcano, besides Mount St. Helens, to erupt in the continental United States in the 20th century. The eruption, which occured in 1915, was visible from Sacramento, several hundred miles away. Because of its recent activity, Lassen is the center Lassen Volcanic National Park (California has more national parks/seashores than any other state).
Lassen:
The 1915 Eruption:
Moving away from mountains, California has other natural features that set it apart from other states.
The Pacific Coast:
The coastline of California is one of the most rugged anywhere in the world. North to South, it's mostly cliffs and rocks. In the North, you have the Lost Coast, a stretch so rugged that it was deemed impossible to build a highway across, and thus the storied Highway 1 was moved inland here.
You also can't forget the Marin Headlands, north of San Francisco. Very beautiful in their own right.
Marin Headlands (with SF in the background):
Moving further south, Big Sur is one of the most famous, and beautiful, sections of coastline in the country. This is truly where the mountains meet the sea, and features some of the tallest coastal mountains in the world, as well as stunning waterfalls and breathtaking vistas.
Big Sur 1:
Big Sur 2 (with McWay falls, 80 feet high, for scale):
Moving even further south, the Channel Islands are absolutely amazing, if you get a chance to visit them. I've spent some time on Catalina Island, and it seems to be the closest thing to the Med as you're going to get without flying to Europe. Catalina Island, a member of the Channel Islands, is home to a herd of buffalo, several cattle ranches, some of the best swimming on the Pacific Coast, and is navigated mainly by golf cart (from what I can tell).
Avalon (on Catalina):
Besides geographic features, California also has a wide diversity of wildlife and plantlife. California is home to the Tallest, Largest, and Oldest living things on the planet, all trees.
Wildlife:
The Giant Sequoia are the largest trees (and thus living things) in the world, and grow natively only on the western slope of the afformentioned Sierra Nevada. The biggest of these, the General Sherman tree, is 274 feet tall, 109 feet in circumference, and has a volume of 52,584 cubic feet.
General Sherman:
The Coast Redwoods are the tallest trees in the world, and are located on the coastline (as their name would suggest) of Northern California. The scenes in Star Wars: Return of the Jedi of th Endor Moon were shot in Jedidiah Smith Redwoods in Norther California. The tallest tree currently known is Hyperion, a coast redwood in Redwood National Park, and stands 379.1 feet high.
The Lost Monarch:
The Bristlecone Pine is the oldest species of tree (and thus living thing) known to man. These trees exist only in Eastern CA and Western NV, and can reach ages approaching 5,000 years. That means that some of these trees were saplings almost 3,000 years before the birth of Christ, and have been alive since before the Pyramids were constructed.
Bristlecone Pine:
The Desert:
Lots of people don't like the desert, and I can understand why, it's too hot, dry, and inhospitable to be comfortable, but one shouldn't write it off. It has its own dramatic beauty that can't be overlooked. California has some of the most dramatic deserts in the world. The most famous is Death Valley National Park. Death Valley is the lowest point in North America, at 282 feet below sea level, and is one of, if not the, hottest place(s) in the world. The record temperature here is 134 degrees Fahrenheit (taken at Furnace Creek, which is typically several degrees
cooler than Badwater). Telescope peak, directly adjacent to Badwater, also features one of the most stunning elevation gains in the world, roughly equal to Everests' rise above the Tibetan Plateau.
Telescope Peak from Badwater:
The Alabama hills, between Lone Pine and Mt. Whitney, are another stunning desert feature of California. Seen in so many movies, they are practically a Hollywood backlot, the Alabama hills have their own attraction (and if you know what you're looking for, you can identify them in literally hundreds of movies).
Alabama Hills:
http://michaelcadengallery.com/db1/00053/michaelcadengallery.com/_uimages/AlabamaHills38x16.jpg (broken link)
So anyways, that's a very brief overview of the scenic beauty of California. There are thousands of other spots that could be included in this post, but I have neither the time nor the patience to do so. Maybe somebody else could do a brief writeup/photo safari of the cities in CA? Or, perhaps, talk about the importance of the state economy to the national economy (and perhaps, how California is, by far, the most productive agricultural state in the country)? I think I've said enough.