Yes, almost any knife can be used as a fighting knife when needed. However, there are certain knives made for the art of combat that stand out as being much more purpose-driven. This is proven out by those that use them in the field for their intended purposes, the military.
Even so, the actual fighting aspect was probably a secondary, although the incredibly important reason for using this purpose-built edged tool. There have been a number of knives designed to be used in close combat. And each fighting knife is usually designed for delivering thrusts to the vital organs and such or to slash at exposed targets.
Traditionally, they are of dagger or stiletto types and are designed for thrusts. The best of them have sharpened edges so a slice can be utilized as well. A crossguard is a good idea as well to help parry opponents blades and keep your hand in place.
A proliferation of fighting knives was seen during the two World Wars. WWI had bitter trench fighting. So vicious was the combat in the trenches that such knives (with brass knuckles incorporated) really did see action. Nasty for sure. The most famous is probably the US 1918 pattern dagger with its 6”-7” double-edge blade, brass knuckles, and skull-crusher pommel. The next famous during this time was probably the British Robbins of Dudley knuckle knives and push daggers. So good were these designs you can find them in later use in WWII and Korea.
The kukri, developed in Nepal was a multi-purpose chopper used in combat by the revered Gurkha Regiments in Asia and wholly endorsed by the British Empire. The heavyweight, forward design along with massive belly made it vicious in a swing. These were used heavily in the 1800’s to 1900’s in various parts of the world and are a favorite today by campers and Hollywood.
Knives that stood out from WWII with the classic fighting double edge, stiletto shape, and dagger proportions were the Fairbairn-Sykes, the V-42, the M3 Trench knife, the M4 Bayonet knife, and the Applegate-Fairbairn. The M3 and M4 seeing the most use due to them being standard issue to US troops.
An all-around knife used for fighting and heavy camp work was the Smatchett. A large, long, wide blade made chopping easier. It was great to fend off an attack but also excelled at digging and building encampments.
There were clandestine knives from the Special Operations Executive and the CIA. These knives, usually smaller and sewn into a lapel or cuff/sleeve, were designed for assignation more than outright fighting.
From WWII to now we’ve had some impressive companies and custom knife makers stand out with fighting designs that have proven their worth on the battlefield. Both Randall and Ek knives are tried and true. Those that have them swear by them with their lives. Companies that held long-time military contracts in the US have a strong reputation for effective and time-honored designs as well including Ka-bar, SOG, Ontario, and Gerber.
If you can get your hands on any of these, you’ve not only got a great fighting knife (in the right hands) but more times than not, a collectible which can prove its value in the field and hold its value or even appreciate in the collector world.