I play Heimerdinger like an assassin.
I wait till the teamfight has gone for a few seconds, hop in from side, R W QQ E, they should be dead if you farmed/built good enough.
Also lol...
me: "you guys lost because you have too many carries"
enemy team (aka just ashe): "its all mf's fault never did anything"
>looks at graph, mf did almost as much phys damage as ashe (the one complaining) (don't say it's because of her W, E, and R, because those do magic damage)
>looks at fiddlestick's cs, which was less than 100
>remembers teamfights, where ashe point blanks me (tank) with ult during teamfight and focuses me for some reason
>remembers who was pushing lanes to take our turrets (hint it wasn't ashe, it was sion, sivir, and surprise miss fortune!)