I have two Titanium bicycles and a ring. The ring is beautiful, lusterous and keeps it's polish. It resists corrosion as well as the gold inlaid on it's surface. It's not cheesey, it's a nicer looking material than platinum.
The titanium bikes are also unpainted. Titanium has wonderful ride qualities as it gives you back all the energy you put in. About as stiff as steel, almost as light aluminum and carbon. The most delicate part of a frame, the dropouts where wheel and deraileur connect, are extremely crashworthy. One manufacturer has never seen a broken one. You can't say that of any steel bike. Needless to say, the bike industry is alot more innovative than the gun industry.
Titanium would be great for a long slide pistol. Instead of cutting holes in the slide (Glock 34), you just make it in a less dense material.
It would be perfect for frames. No galling, no corrosion, no finish wear. It would probably have a (minor) recoil damping property.
The only thing Ti isn't good for are cutting surfaces. Rifling is essentially a cutting surface.