RTS/RPG SpellForce 3 just put out a pretty slick looking map editor today. Not only can you create maps using the same tools as the devs, they also included a scripting tool to create your own missions and custom maps. If that isn't cool enough (and it is, check out the trailer below, this looks badass), you can also use unique rule sets for your god-like creations. For example, if you want to set up a MOBA style map, where you can only command heroes while automated armies brawl it out, then, well, cool, do it. Or maybe you wanna go for a more Horde like map, where waves of increasingly difficult enemies flood the map to take you down. That? Is also just fine.
The modding tools are free for owners of Spellforce 3, and you can downloaded them directly from Steam right now. For you noobs, the map- and scripting editor comes with a detailed tutorial and glossary, so even the rookies can enjoy the insanity.