Next week I'll be attempting something new. I will be running an adventure for my D&D campaign without using a published module. Over the years I've run homebrew adventures a gajillion times, but this will be my first go making something completely from scratch for these 3.5-powered 12th-level Gestalt engines of destruction. I've spent the last week or so tinkering with NPCs, adding class levels to monsters, and tweaking critters using the methods outlined by Mike Mearls in the opening chapter of FFG's Monster's Handbook. Another product that has proven helpful in this endeavor is the PCGen character creation software. Due to my ham-handed approach the resulting builds will probably be a bit crude and the adventure will be simplistic, but I'm pleased at the prospect of whipping together a whole session of material starting with nothing but a couple goofy ideas.
Here's a teaser for my players: there will be robots.