This is an interesting question and I've seen versions of it posted several times. If you define modern as 20th century, then there are numerous men from the American West, from 1805 until about 1870, who fall in this category. They often held a mix of jobs, freelanced or did contract work, were soldiers, scouts, professional hunters and trappers, Indian fighters, etc.

Without knowing whether you're interested in them (or whether you're considering pre-modern to be before ~1500), I'm not sure how much detail to give.

The Lewis & Clark expedition was a government-funded expedition across the Northern Rocky Mountains to the Oregon coast, and back, kicked off a boom in the fur trade, causing hundreds of men to start trapping, hunting, and exploring the Plains and the Rockies, starting in about 1807.

John Colter was a member of the expedition, and before the expedition got back, he was honorably discharged in North Dakota and joined up with two beaver trappers to lead them back into Montana. He later became, probably, the explored the area that is now the Grand Teton National Park, possibly parts of Yellowstone, and probably Jackson Hole. He was probably the first White man to ever visit parts of Yellowstone, and he reported of unimaginable geothermal activity in that area. He traveled hundreds of miles in the winter by himself. He both traded and helped Native American tribes, and also fought other tribes.

Kit Carson was in the second wave of trappers. He was mostly in New Mexico and the southern Rockies. He went on trapping expeditions, fought the Apache, explored into California and Colorado, went on rescue missions, etc. As a mountain man, he had to hunt for his food, and fought grizzly bears. He worked as a professional hunter (shooting game to feed settlers) at one point, and was in the military during the Mexican-American War and for the Union during the Civil War (during the brief New Mexico campaign). He was hired by the government as a professional scout for 3 of John Fremont's expeditions mapping the west.
He was involved in many skirmishes/battles with various Native American tribes, and was later an Indian Agent for the government. He fought in the First Battle of Adobe Walls in Texas against the Kiowa tribe, and led some brutal/harsh campaigns against the Apache and Navajo (basically, genocide). He could not read or write but spoke English, Spanish, and several Native American languages. He was married thrice; his first wife was Arapaho and he fought a duel against a French-Canadian to win her hand in marriage. His second wife was Cheyenne tribe. His third wife was Hispanic/Mexican woman. Blood and Thunder by Hampton Sides tells his story; it's an epic tale and so crazy that it seems like fiction. https://www.amazon.com/Blood-Thunder-Carson-Conquest-American/dp/1400031109

Jim Bridger spent about 20 years blazing trails, trapping, guiding, etc. all over the northern Rockies. He was probably the first White man to see the geysers of Yellowstone. He explored the Great Salt Lake. He also fought bears (common thread with these guys). He was hired as a guide by various parties and was a scout for the government during Red Cloud's War.

These are just three of the dozen or so famous mountain men. This era sorta closed by about 1840 or so, as the beaver population declined and the price of pelts collapsed because men's fashion turned to silk top hats rather than beaver pelt hats. After the Civil War, there were other waves of settlers and men who also provided various contract mercenary type skills (scouting, guiding, professional hunting, providing security to stage coaches, etc.).