Before you buy a handgun, go to your local firing range that has rentals and try them out first. Pick a gun that will serve your needs. Listed in no particular order:
1) If you ever think you'll need it for home defense, when it's dark, get one with tritium night sights.
2) Pick a caliber that you can handle without discomfort as you'll only be hitting much lower than your aim as you'll probably be flinching (pushing forward and downward in anticipation of the recoil).
3) If you'll be carrying it, you'll probably want a lighter-weight handgun.
4) Your choice MUST be reliable. Your last words on earth after your gun goes 'click' instead of 'BOOM' don't want to be "Oh toejam!"
5) Accuracy is also important as you need to hit what you're aiming at.
6) Practice...practice....practi ce! You won't do anyone (particularly yourself) any good if you cannot load, cock, and fire your weapon as you intend to in a stressful situation.
7) YOU MUST ALWAYS PRACTICE SAFE GUN HANDLING! If you cannot, do everyone a favor, don't get a gun.
8) Also store your gun properly. It's not going to do you any good if it is stolen by a drug-using thief that broke into your house while you weren't there. Also you don't want kids finding it and shooting another because they had access to it.
9) Also if a home self defense gun, how many neighbors live around you? Every stray bullet is a law suit ready to happen. You need to consider that you might have to kiss your house, car, and future earnings bye-bye to your neighbors sueing you in event of bullets going into and/or through their dwellings. Especially if you happen to accidently hit innocent bystanders.
Check out and research all the guns listed by others in this thread. Most are good choices. I have a SigSauer P220 45acp with Tritium nightsights. Extremely accurate and reliable, plus fairly light-weight (26 oz empty). I love it. Again it is MY choice which might be different than YOUR choice. Good luck in your search.