There are so many great 9mm pistols out there that it's hard for me to narrow it down to just three (which may explain why I own five.) But if pressed...
1) Beretta M9. Yeah, it's the world's biggest 9mm (or at least it feels that way.) Not many folks are going to conceal it, but it's a fine service pistol, a good shooter and as soldier-proof as a pistol ever was. I enjoy taking mine to the range and I'd trust it in any situation.
2) CZ 75B. Hand, meet glove. When a gun fits you this well and recoils so gently, it's almost impossible not to shoot it well. In matte stainless, it's almost a work of art. Sometimes I think it's too pretty to shoot. Sometimes.
3) Browning Hi Power. If the FAL was the right arm of the free world, the Hi Power was the sidearm of the free world. In world of DA/SA triggers, striker-fired guns, and polymer frames, it can seem outmoded, even quaint, but all that goes away when you lay the sights on target. It's a timeless classic.
Others in my collection: the SIG P6 represents the traditional DA/SA SIG 9mm pistols. All are quality weapons. My P6 was made the same year I was, but it hasn't aged a bit. The H&K USP9 is (along with its big brother the USP45) my concession to the polymer age. It just shoots so well that I can't ignore it.
But if I were going to carry a 9mm, it would probably be one I don't currently own - the H&K P30, the only polymer gun I've ever found with finger grooves that fit me. Light, reasonably compact, accurate, and reliable, it would be my first choice for a CCW 9mm.