Adding my below post from another thread to this one - since this is a nice summary of lots of others.
Heimer's oringal niche (long before I played LOL) was that he could push towers like no one else - which anyone that owns Heimer now is no longer the case. They need to re-do/buff him, but first they need to decide WHAT they want him to be. Do they want him to be a tank, AP mage, support, jungler? Personally, I don't care as long as they do something to make him useful, while still being fun to play (the entire game, not just the first 10 minutes or so). Hell, make him a support champ, and change his abilities to support teamates, and I might actually like that role.
Although if they made him a tank, a "Tankdinger" skin would be cool, where he drives around in a little tank that shoots, rather than tossing wrenches around....