At Rite Aid they have generic Lego style figures for $1.99. The figures are crap but the weapons are pretty snazzy. Some of the weapons made for brick figures don't require any kind of modification to work with Joes. While others are completely out of scale. But some of the pistols and small automatics work really well for 1/18th scale figures. You just have to do a quick mod to the grips.
This is something I've been doing since I discovered BrickArms.com several years ago but never thought to bring up because it is so easy. You take some vice grip plyers and simply squeeze. It squishes the plastic down flat. Sometimes I'll even get fancy and try to give the weapon a cross-hatched grip appearance by going diagonal one way and then the other. Seriously, 10 seconds tops for this one.
I didn't think to snap a pic until after I did the pistol but the MP 5 is right out of the box.

Squishy squishy

Flatened grip with hatch marks.

In a figure's hands for scale purposes.
