No mods on my Glocks, just Trijicons on my CC G26 and factory stuff on the others. The stock Glocks rock outa the box for me. The only thing I would really consider doing is adding the smooth aluminum trigger for my G26, but that's just about it.
Mods to my Glocks:
Tru-Glo TFO sights (bright under all conditions)
Crimson Trace laser
Vicker's Tactical extended mag catch (just a bit longer than stock)
Pearce +0 pinky extension on my G26 mags
extended mag drop
CT laser on 27
pinky extensions on 27
houge slip on on 23
polish all trigger parts
TruGlo TFO night sights (green/yellow), Lasermax guide rod, smooth trigger, Hogue Grip Sleeve, high-grip (undercut) trigger guard mod.
G 26 stock - Night sights soon.
I just have night sights on my Glocks and my G17 has a Hogue grip sleeve. The rest is factory.
The only changes I did to my G30SF was to put a smooth faced G21 trigger on it and XS Big Dots. On my wife's G19 all we did was buy it with factory installed Trijicons.
I have the following parts installed in every single Glock I own.
(1.) Tango Down / Vickers Tactical extended mag catch
(2.) Factory Glock extended slide release / slide lock lever
(3.) Factory Glock 3.5lb. connector - everything else stock
(4.) Jentra plug
(5.) Factory Glock smooth face trigger on my G19's.
Fixed: Heinie Ledge or Warren Tactical
Adjustable: Dawson Precision adjustable target rear sight / Dawson Precision Ramped Serrated plain black front sight.
Every one of them as proven stone reliable and adds something without effecting reliablity. Which is a must for me.
Nothing except for sights and then it's TFO's all the way. Otherwise leave it as designed, Glock Perfection!!!!