Fans have been modding the excellent shooter Serious Sam 3 for awhile, but now it gets better and easier, because Steam Workshop support has been enacted.

If you're still somehow ignorant to the wonder that is Steam Workshop, it's a system available on -- go figure -- Steam that lets you search for and download mods, then subscribe to them for automatic updating, and do a bunch of other interesting stuff.

If that sounds interesting to you (and it should, if you ever want to shoot monsters with distinguished monsters with top hats and monocles in the face with a double-barrel shotgun), hit the source to get started.