Beyond coatings to reduce shine and protect against the elements it's marketing hype. Even then any type of knife could be considered a "tactical" knife.
Even the big manufacturers perpetuate such terms even though they may not use the term "tactical" expressly or overtly.
Benchmade's Black Class:
"Used by professionals when quality tools can mean the difference between life and death. From law enforcement and public safety to elite military troops, our obligation is still the same: The best equipment for the job. Imagine what they can do for you."
Spyderco's OpFocus Catalog:
"OpFocus, short for “Operational Focus” is a term that we coined to accurately describe a view of our products from the perspective of the duty-bound armed professional, first responder, martial artist, or defense-minded civilian. The Spyderco products featured in this catalog were selected from our comprehensive product line as those best suited for mission-oriented tactical applications. They include most of our CLIPIT™ models—the original one-hand-opening, clip-carried folder that literally defined the form of the modern tactical folding knife more than 30 years ago. The OpFocus catalog presents all these products in a context and format that enables you to quickly and easily compare them so you can choose the knives that best meet your needs."
Zero Tolerance:
"Designed and manufactured to stand up to hard use, ZTs are built of technologically advanced materials including S30V, ELMAX, or 154CM blade steel and 3-D machined G-10 and titanium handles. These proudly overbuilt knives have earned a reputation among their devoted fans for being “built like a tank” or “a real beast.” Zero Tolerance made its first appearance in 2006. Initially, these ZT are made-in-the-USA, hard-use knives were designed to meet the needs of professionals, such as the military, law enforcement, as well as other first responders, including fire fighters and emergency medical personnel. Today the line has expanded to include a variety of general-use and premium knives. And while many ZTs are larger, heavier knives, some customers won’t have anything else as an every day carrying knife. In addition to their “built like a tank” construction, ZTs have also been recognized for use of the most advanced materials and technologies. Call it dedication. Call it obsession. Whatever it is, it’s something we intend to keep on doing so we can keep on building the kind of premium-quality, professional knives that ZT customers can depend on every single day."