These days you can't talk custom LEGO minifigures and accessories without mentioning BrickArms.
I think Will Chapman, owner and founder, summarizes it best at BrickArms.com:
"BrickArms LLC is a small toy company specializing in original, custom designed LEGO® compatible weapons and custom minifigs. All toys are original, and we produce high quality, low cost toys that "fit" perfectly with the LEGO-Universe."
For those who don't know, there has been a long standing tradition at The LEGO Group to not have minifigures use guns or weapons of war. With newer, licensed-themes TLG has relaxed its stance, but still holds its ground on some items. BrickArms has seen this as a market opportunity and has carved out a nice niche within the custom minifigure community.
Recently (February 2010) Wired Magazine featured BrickArms as an example of the "New Industrial Revolution". The article focuses on the DIY, micro-manufacturers who are making products (and profits) right in their own garage.
There are some signs that TLG is starting to take notice. The Toy Story soldier pack can easily provide the makings of WWII soldiers, while the Roman soldier scheduled for the Series 2 collectible minifigure collection can be the flagstone in your new empire. However, a TLG approved AK-47 is not likely to appear in any official sets soon.
If BrickArms sounds like something you might be interested in, feel free to drop by or to read the Wired magazine article.
(Pictures from BrickArms.com)