It depends on the purpose of the gun. For carry, I really like the 19, but my wardrobe lends itself to carrying larger pistols. Lots of folks prefer the 26 or 27.
For a new carry gun, look at the G43. I think I'd rather have the S&W Shield, but the G43 is very popular.
For a new range gun, I'd be looking at the 17 MOS or 34 MOS. Not that I've ever even seen one up close, much less shot one, but they seem like they'd be fun at the range.
For a new farm/truck gun, G21. It's hard to argue with 13 rounds of .45 acp, and I've found the G21 to be a pretty soft shooter.