Whatever is easily concealable and comfortable to you. As mentioned earlier, weight is the biggest negative factor in my opinion. My most common carry guns are: 1a) Colt Defender in .45 ACP...all the knockdown you could ask for, yet still light enough not to be cumbersome to me, and 1b) Sig P238...1911 format in .380 ACP...light as it gets, great shooter and you can hide it even if you're out in your boxers.