Ah, I had assumed that he was an experience shooter.
Vito, if he has not already made a decision, do this:
1. Find out if there are any restrictions (make, model, caliber, action type, etc). I find it hard to believe that a modern LE agency does not have SOME restrictions. That will narrow the field considerably.
2. Ask what calibers, if any, the LE agency will provide. That might not be a limiting factor (it's up to him and his wallet), but it's nice to know.
3. If it is still up for grabs, limit yourself to major calibers. 9mm, .45 ACP, .40 S&W, .357 Sig and maybe 10mm for autoloaders. If he is a revolver guy, consider .38 Spl, .357 Magnum, .44 Magnum. As nice as .38 Super and .41 Magnum are, he'll go broke feeding that gun, and he wants to be able to
practice. So, stick with common calibers.
4. After that, he needs to go shoot a lot of guns. In pretty short order he can figure out what works and what does not work for him. While extensive training would be nice before this point, it's not really required. If it feels bad in the hand, it is bad. If he cannot reach the controls, it is bad. If the procedures to load and fire seem too complex (some people hate manual safeties), it is bad. If recoil seems bad, it is bad. After fingering, dryfiring and live firing a bunch of guns, he will be able to see what he likes and does not like. He can trust his gut on this one. A gun that feels poor in the hand can be made, with practice, to feel more natural, but the opposite is not true; a gun that starts out feeling right will probably not get worse with practice.
5. Stick with major makers. Glock, Springfield, S&W, Sig, Ruger, Colt, Kimber, H&K, Beretta, FN/Browning, etc. If you've never heard of the maker, that might be a sign.
Of course, you're looking for suggestions. Consider these, but if they don't fit, don't sweat it.
Glock. They're all the same, except for details like caliber, barrel length and grip size.
See which one he likes.
Springfield XD. Great gun, may or may not fit his hand.
1911. There is a reason why this gun is alive and kicking, coming up on its 100th birthday.
Browning Hi-Power. My first gun. It just feels right. Available in 9mm and .40S&W.
S&W M&P. New, so it does not yet have a track record, but early reports are pretty good. Nice trigger, feels good in the hand.
Mike