While it might be over three years old at this point, Saints Row IV is still going strong on the PC. The modding community has been providing new weapons, outfits, and more for the title for quite some time, and now, that content can get added to the game directly from Steam as Workshop integration is available.
At the moment, there are 26 items available in the Workshop. Most of what's there are new outfits, but there are a couple weapons and some cheat mods in there, too. If you don't currently own the game, now is a good time to pick it up as it's 75% off on Steam. This includes the "Game of the Century Edition," which includes all DLC for the game, so for just $4.99, you can get more content than you possibly experience during a long weekend.