I couldn't imagine changing what they got right from the factory. I can see how people would like to personalize theirs though. Like the slide release lever, magazine drop, or trigger to their liking. Though I do have a houge grip on my 2nd Gen 19. Does that count as a mod?
My main carry guns are all stock besides night sites except the 20 she has no night sites yet, the 20 also has an extended slide release even though it was added by me it wasn't meant for me. My 17 has too much to list but hear it goes....That has a 5" custom barsto semi-drop in 3-slot ported barrel, hard primer striker spring, wolff 17lb spring and stainless steel non-captured guide rod,adjustable trigger ,ghost rocket connecter, extended mag and slide release, tri-jicon night sights. I think thats it. It also has 5 mags.
I just got a Gen 4 G-27 a couple of days ago. It has the +1 extensions on 2 of the mags, extended slide release, Trijicon night sights(green front, yellow rear), 3.5 Ghost connector, and a 25 cent trigger job.
On mine I have a KKM G35 SS match grade barrel, SS guide rod w/factory weight spring, extended slide lock, extended slide release, extended mag release, grip plug, night sights, 31 round magazines, and the frame is Duracoated Sniper Green.
I started changing some stuff for a reason. I got the mag release & slide lock because I have really small hands (I still have to cant the gun to depress the mag release even with the extended one). I got the grip plug because I was going to carry it and didn't want lint and stuff getting in there. I got the barrel because I shoot home loads. I got the mags because less reloading is nice. I got the guide rod because the factory plastic one started to look like it was fatiguing and I just didn't wanna chance it if it was. I got the slide release because I like options, and I duracoated it because it looks good.
It's not super trick but it is fun at the range. My carry is factory.
Pearce grip plug
Hogue grip sleeve
4lb Striker Spring
6lb Trigger Spring
Reduced Power Safety Plunger Spring
White painted letters on slide and all mags
Boba Fett Mandalorian skull slide plate
Extended slide release
Extended slide stop
Extended mag release
Pierce +0 extension on 2 mags
Pierce +2 extension on 3 mags
and... BEST MOD EVER!!! Thousands of rounds down range and probably even more practice in my living room drawing and dry firing. People say you cant be too accurate with a G27... LIES!!! Im a straight sniper with my baby Glock. lol
Next up... night sights and probably a tungsten factory spring weight guide rod.... gun show this weekend to hopefully end my search.