This is by far the best free game I've ever played. Map Editor, FFA or Team battles, and extras to download.

StickSoldier home page (http://www.sticksoldiers.tk/)

I'm not that good yet, but I've made some good levels.

I have some tips for those who have difficulty making levels, to save it press ` and then press save title. To give it a name, press mapname title, where title is the name you want.