Since you have only a $300 budget to work with a new S&W or other "top" brands are out. A used handgun isn't a bad idea but you will have to look around for something you like and feels good in your hand.
If you want to buy new then I will suggest buying from Taurus.
If you are looking for a pistol then I suggest a Taurus PT-111 Pro. It's a consealable 12 round 9mm semi-auto that's reliable and accurate. They list for just over $400 but can be found NIB for ~$300.
http://www.taurususa.com/products/product-details.cfm?id=24&category=Pistol
http://www.taurususa.com/products/product-details.cfm?id=18&category=Pistol
If you are looking for a new revolver, Taurus makes many different models that will fill your needs. Their Model 650 in .357 Magnum and Model 850 in .38 Special are also reliable and accurate, not to mention a lot less expensive than S&W.
The link below are for their "CIA" models which are like S&W's Centenial frame.
http://www.taurususa.com/products/gunselector-results.cfm?series=CIA2
Their Protector models, Model 651 and Model 851 (S&W Bodyguard frame) are also available in the same price range.
http://www.taurususa.com/products/gunselector-results.cfm?series=PR2
If you don't intend on carrying the handgun and want it only for Home Defense look around for a used S&W 4" Model 10 (.38 Special) or a 4" Model 19 (.357 Mag) They can be found in your price range.
I know there are as many suggestions as there are people on this forum. The suggestions I made are just what I would do in your situation and are only suggestions that may or may not be right for you. I hope they help you in making a decision on what to buy or at least give you some options you might not have thought of.
Good luck, be safe and by all means, have fun!!