Well...

You can take a cheap ($3 or thereabout) Mini-Maglite knockoff - made in China probably, they've been around for a long time now.

It's about the same size as hi-tech LED lights and has a solid aluminum body. No, it doesn't look as tactical as that Hellfighter thing with spikes. But if you have to, you can easily make neat holes in drywall with it, smash a window or somebody's skull if it ever comes to that. I don't think you'll notice any difference at all in that department between the $3 knockoff and a $150+ Surefire.

I wouldn't count on any light (regardless of the brand and price) still working after you put it through that kind of (ab)use. Then again, if I ever have to beat someone into unconsciousness with a flashlight, whether the light still works once I've accomplished the deed is not going to be my main concern.

If self-defense is that much of a priority though, I think there are better options out there than a tactical light. And if it absolutely has to be a "fighting" flashlight I'd personally go for the biggest, heaviest Maglite out there. YMMV.