Funny combo, but not the best you could think of, yet quite powerful in early game is Dark Seer and Gondar (or any other invisibility hero). You just put Ion Shell on the other hero, wait for HP to come down a bit and just gank. Easy kills, because usually people don't realize what is happening.
I think I saw something like this happen once in one of those dota fail videos on youtube.
It was a veno and some other hero that I don't remember. They were taking damage over time from an invisible unit, and only when they got to half of it they started running away, the venomancer dying.