Buyer beware but on the other end of the spectrum, you can find some smoking deals at pawn shops. As posted earlier, do your homework. Go over the gun and make sure it is mechanically sound before starting a conversation on price, take a bore light if you can. Get an ideal of the going rate in your area for the particular gun you want.
I have on occasion paid what was on the price tag, simply because it was more than a fair price, actually a great price in some instances, but I always ask if they will at a minimum eat the sales tax. That being said it doesn't hurt to ask for a price reduction. I always phrase it as what is your Out The Door price, this will encompass taxes 99% of the time. As listed above, don't be a smart a**, have cash and don't be afraid to counter offer and if you make the offer and they accept it, pay up. If they won't budge and the price is too high, walk. Wait a few months, if it sets there 6 months, 8 months, go back in and make the same offer, they may very well take it this time around. I waited one pawn shop out a year on a mossy slug gun. It was $60 over priced and they wouldn't budge, one year later the price came down $50 and I walked out with it.
Understand they are there to make as much money as they can.
Good hunting!