Personally, but for most people I'd rec a small, single stack 9mm that's DAO or striker fired. Some of the better known 9mm single stack mag guns in this category are Kahr CW9/PM9/CM9, Ruger LC9/LC9s, Walther PPS M2, S&W M&P Shield, Springfield Armory XDs, Sig 365, Glock M43 and Beretta Nano. For those willing to adequately learn the SAO platform, I'd throw in the Sig 938/Kimber Micro 9/Springfield 911 9mm as well as a reliable 1911 (either Officer or Commander size). Most of these guns will be carried inside (or outside) the waistband; some of the smaller single stack 9mm's (like the CM9) can also be pocket carried in some pants. Remember that for IWB cc, you'll need to wear pants that are 1-2" bigger in the waist.

If you intend to cc outside the waistband (OWB), I'd look at the double stack mag guns. I started off w/ IWB cc, but now use OWB more of the time. In this category I'd include the various compact and mid-size Glocks, M&P's, XD's, Canik TP9 Elite SC and DAO Sig Sauers. Some like to cc a double stack gun IWB. I tried it for a while w/ my first cc gun (SA XD 40 S&W) before quickly realizing it was NOT for me.
I'm sure I've left off some good ones, but these are the first that come to my mind.
The main thing is to find a reliable gun that handles well for you. Glocks are VERY good guns, but they don't handle/point well for me. If you don't like the trigger, instead of modifying it I'd suggest getting a different gun that has a trigger you find acceptable. Also decide what type of features you want your gun to have. If you want an external safety lever, then it won't be a Glock. If you want a grip safety, your gun will have to be an 1911 or an XD/XDs. If possible, handle as many as you can before deciding on one.

Most importantly, you want a safe and reliable gun that you shoot well and is comfortable enough to carry so that you'll be willing to wear it. Keep us updated.

I didn't even mention revolvers since you've already settled on the 9mm, but forgot that Ruger actually chambers their fine LCR in 9mm.