One category of novel that has been generally out of vogue because of low sales is western fiction. Sales increased by 7% in 2014 but are still low overall. If you write westerns, you write for a niche market, but readers of westerns are die hard for the genre, and if they like you, they really like you.
There are several categories of western novels, but the general definition is fiction set in the 19th century frontier or Old West America, west of the Mississippi. The characters are strong and self-reliant, and the stories usually involve cowboys, calvarymen, lawmen, and outlaws. Generally, western novels focus on themes of individualism and adventure. Westerns generally feature a lone hero (usually male) who reluctantly answers the call to adventure, rescues damsels in distress, and brings the bad guy(s) to justice. The hero is idealistic and driven.
Anti-hero: The anti-hero has opposite attributes to the standard hero character and may be an outsider to the standard setting.
Bounty Hunter: The bounty hunter makes a living bringing the bad guys in for reward money. The character is usually cynical, and is often perceived by society as little better than the bad guys he arrests.
The Drifter: The drifter wanders into a troubled town, and is hired by locals to the law.
The Gunslinger: The gunslinger is often tied to the drifter, who is out to do good. Sometimes the gunslinger is a dead shot, quick draw kind of (usually) guy.
There are westerns with female protagonists, but these seem to be few and far between.
Many western tropes are blended with other genres (think Firefly which is a western story set in space), but the three tropes listed above seems to be the most common. Blended subgenres of course include: cattle punk (western scifi), weird west (supernatural), and samurai cowboy (feudal japan) to name a few. These are usually marketed under speculative fiction, or romance, etc rather than marketed as western fiction.
Just because western fiction sales are slim, doesn’t mean you shouldn’t write western fiction. If you have a story inside you, take the time to figure out the trope you want, create intriguing characters, great action, and a great plot, and write it. Readers of western fiction are looking for more novels. And maybe your book will trigger a revival of the genre.