Had a sweet encounter today at KNFE (NALF Fentress). Was coming into the overhead at our normal 350 KIAS to join the FCLP pattern. About a mile out I see a Cessna 172 co-altitude (at overhead break altitude) with me, and not moving on the canopy as he crosses perpendicular to the runway. Had I not seen him, we would have had a horrible midair over the numbers. VFR, not talking to anyone, not squawking, just trolling right through a nearly full traffic pattern (5 jets). I don't know what my PSA really is, aside from just not being an idiot. Maybe he was just trying to get up close to have a look, but he took absolutely no evasive action (I can't imagine him not seeing me, but he acted like he didn't) and I had to aggressively avoid him vertically while still trying to pick out everyone in the pattern and find my interval out of the break. Granted it isn't controlled airspace so I'm not sure if he was actually violating anything other than poor visual lookout/see-and-avoid, but it was potentially one of the dumber things I have seen someone do in an airplane. Anyhoo......just venting.