It is unbelievable how many choices are thrown at us nowadays. There have been some great guns mentioned in this thread, but I am a handgun fan and this is how I look at each of my purchases.
1) Price. In my opinion, the number 1 factor. You need to set a price range and stick with it. This will rule out some guns, but thats good because it reduces choices.
2) Application. What will this gun be used for? Again, so many uses, that are dictated by caliber and frame size. I carry all of my guns, at some point or another, but always have a favorite “go to” gun as the seasons/locations change. For instance, for a daily carry I enjoy my Glock 27, which is the subcompact .40 cal. This is also the gun I practice with the most. When I hunt, camp, hike, or fish, I carry my Glock 20, in 10mm. Again, different applications = different gun.
3) Caliber. This goes with application, and price. I’ve owned a variety of platforms, calibers, and manufacturers. If I have one bit of advice, stick with one or two calibers, even if you switch platforms. This is difficult, and has been for me, but I can keep an accurate count of ammo/reloading supplies. If I had to pick one caliber for semi-auto it would be .40 cal. For revolvers? .357 for the win. They are adequate for my purposes, and have served well in their applications.
I apologize that this is so long-winded, but I’ve been in your shoes many times and this has helped me along the way. Oh, by the way, get a Glock 
