First of all, which end are we looking at?
The only gun I want to see the barrel end of is one that I've just personally verified is unloaded...
While I have seen some absolutely beautiful individual examples of custom guns, here are my top five production pistols rated purely for visual appeal (at least, of the ones I can think of off the top of my head):
1. any Glock - the Glock design has a simplicity of form that could only be improved by making it out of stainless steel rather than polymer, but even in plastic, it's still the best looker to me.
2. Walther PPK or PPK/S stainless - hands down the most beautiful all-metal autoloader ever made
3. Beretta 92 or 96 stainless - the best looking full-size service pistol, with a perfect balance of curves and straight lines without too many appendages to distrat from its form
4. Beretta 84 stainless - for similar reasons as the 92 and 96, a close runner-up to the PPK
5. SIG/Hammerli Trailside - the best looking .22 LR pistol, to me. I especially like the all-stainless versions with the colored grips.