In addition to the normal Glock 23 (13+1) or Taurus PT111 Millennium Pro (12+1)...
-Streamlight Scorpion X (200 Lumens, one of the smallest, high-output, high-battery life, and effective lights around. Excellent for late night or early morning activities... during the day there really isn't a need.)
-Spare Magazine (Depends on what I'm wearing, or if at work concealing. Generally I like to have an extra mag, sometimes two, just to have available. Glock is always filled with Winchester Ranger 135 gr. JHP's... which are nasty, nasty rounds... or Speer Gold Dot 155 gr. JHP's. I've tested many, many rounds for ballistic performance and expansion, and these two are by far the best, even compared to some of the more expensive defense rounds.)
-OC Spray (Again, this depends on the day. I usually don't carry OC spray, but if I'm walking the dog or going out in large public areas where I'd rather not draw, I'll bring a can of liquid hell.)
-Handcuffs (No, I'm not a police officer. No, I never show and rarely carry these in public. I will, however, carry these on my duty belt for private security training, which is frequent.)
-Cell Phone (ALWAYS, ALWAYS, ALWAYS carry your cell phone! You never, ever know what is going to happen. The police, as long as you are within legality, are your friends and you should treat them as such. Thinking that you are a one-man army is not only ridiculous, it's dangerous and you should reconsider carrying a gun if you have that big of a superiority complex.)