The Saturday Night Specials of the 80s and 90s, oft vilified in the news media and by politicians, are still kicking around today. The ol' "SNS" also has a bad reputation amongst the gun-nut crowd--a POS that will jam on you at best, get you blown away in a gunfight at worst.
Of course, the truth lies somewhere in between. Some are complete junk, others are perfectly serviceable firearms. In an ideal world, you'd never need one--you'd have an unlimited budget with which to purchase your defensive guns. But we live in a less than ideal world, and with a crap economy and mountains of other preps to buy, gun budgets are tight. The first rule of a gun fight is to bring a gun, and the cheap-o SNS offers a way to do that.
Would anyone recommend these as a "first choice" for defensive handgun? Nope. But as a gun to bury in the ground or otherwise hide in a small cache? I personally can't see myself burying a $400 or $500 gun. I just don't have that kind of cash to burn, and doubt that most people do. But a $150 gun? That's a bit more realistic.
Many SNS's are also quiet small in size--tiny .22s and .25 ACPs seem to make up a large portion of many gun shops' inventory. Small and easily concealable, pocket sized, with very compact ammunition. You could very easily store a small pistol, pocket holster, and several hundred rounds of ammunition in a very small cache or hiding place. With .22s, you also have a huge selection of ammo to choose from, though most SNSs are picky with what ammunition they will feed reliably.
These little guns are also often smaller than the .380s flooding the market, giving you a concealment option when you may not otherwise have one. While no one will make great claims to the stopping power of these tiny guns in .22 and .25, no one will volunteer to get hit with them, either.
Saturday Night Specials are often disparaged for their reliability, but many of them run perfectly well. The Hi-Point line of pistols are well known for the ruggedness and reliability (as well as butt-ugly appearance and brick-like weight) and run around $130 and come in real calibers like 9mm. The FIE Titan .25 Auto is regarded by many as the "best" .25 Auto pistol ever made and can be had for around $130. Many SNS companies also have good warranties. Hi-Point, for example, offers an unconditional lifetime warranty. So you can't dismiss all cheap guns as being non-functional crap; some will work well. Some, of course, won't. Do your research beforehand.
Don't immediately dismiss Saturday Night Specials, especially if you're on a very tight budget or looking for "backups" to have around or hide away. Of course, don't assume that any of them will work--do your research before you buy and thoroughly test any gun that you purchase.