I'm a "it's a tool box" kinda guy. That is I don't really care what type of handgun must ride in my holster, as long as it works reliably, fires an effective cartridge, and is accurate. I will train with it until I am proficient with it, so make, model, cool factor, and ergonomics all take a back seat (but they ARE still in the car!). That said, I still have my favorites, and I'll break them up into two categories: "On the job" and "personal favorites".
On the Job: Most companies & departments want a DA or DA/SA operation.
Striker fired:
Ruger SR series
Glock
S&W M&P series
Springfield XD
H&K VP
Walther PPQ
Sig 230
DA/SA:
CZ-75 (and clones)
S&W Gen 2&3 (5906, etc.)
Beretta 92/96
Sig 226, 220, etc.
H&K USP
Walther p-5
Para Ordinance LDA
Ruger P-series
Personal Favorites This has some oldies-but-goodies on it, but most would never be allowed by most LE Agencies and Security Companies. Some would be great for CCW, Home Defense, Bugout, etc. Most are military classics. I have left out pistols that are no longer practical combat arms, such as the Mauser C-96, Luger, and Bergmann designs.
Browning P-35/GP/HP
1911 and clones, copies, updates.
Walther P-38
TT-33 Tokarev and clones
CZ-52
Beretta M51
Star Model A/B