I keep having this itch to create my own content,.. but only using existing game content. I remember that Warcraft 2 had an easy editor because all you did was paint the map and then place resources. Far Cry 3 has a nice editor where you can place enemy AI into your map. I haven't figured out how to make the player start the level unarmed though. Arma 2 and Arma 3 have kind of easy editors. Anyone know of any other games that have really easy editors? I've got Skyrim but that editor kind of scares me.

Portal 2. The in-game editor is ridiculously easy, and pretty fun to use.

Legend of Grimrock

I still make a lot of levels for Jazz Jackrabbit 2 using the fun and easy to use Jazz Creation Station.

:-)

Red alert! It's just pop pop pop save start game done.

Made a few maps for Warcraft III a few years ago, always thought it was pretty easy.

Battle for Wesnoth is pretty simple too, after you get used to it.

Cossacks and Age of Empires II have pretty easy in-game map editors.