Heimerdinger is an extremely fun champion that can be played mid or top. Although he is mocked by many, his damage is simply insane. If you know how to play him correctly, he can easily carry a team on his back. If you're looking for a midlaner with nice sustain and sustained damage in teamfights, Heimerdinger is definitely the champ for you. This is my first build and i hope you like it, any feedback is greatly appreciated :) Note: Its is NOT done. I'm just putting something out there, so I can get the feedback to make it better. I will be updating it daily.

Pros

• Great sustain early & late
• Great early power
• This makes him an AMAZING anti-jungler.
• Easiest farmer in the game
• H-28G Evolution Turret are little robots of death
• Hextech Micro-Rockets have amazing range
• Blind will own the ADC
• He's got some kickass skins

Cons

• High Mana Costs
• VERY high cooldowns
• Can be seperated from turrets and raped
• Slow movement speed
• Doesn't get eaten by Chum the Waters
• Cocaine Addict

Turret placement is absolutely critical as Heimerdinger. Correct turret placement is the difference from being raped by a gank and getting an easy double. If the enemy has lots of aoe, do NOT place your turrets in pairs. They will easily take them out and you'll be screwed. I'd recommend placing them either in line with river or behind river, depending on the jungler. If the jungler has nice cc, play more cautiously, but if they don't, feel free to push up lane. Place turrets between the caster minions and melee minions, this way they will be able to take out this wave and the next wave. With the newest Heimer update, his turrets attack what you either auto attack or hit with a grenade.

Heimerdinger does not have too many counters, but a few of them will completely rape him and his little turret family.
Syndra, Very Hard
She will grab your turrets and fling them out of lane with Force of Will, completely disabling your main income of farm and damage. Basically, if you are against a Syndra, GET OUT OF THAT LANE. Unless they are a terrible Syndra, you will die and feed horrendously.
Malzahar, Very Hard
His Malefic Visions basically converts your turrets into gold. This is another lane you should try to avoid whenever possible. If you HAVE to go against him, just play cautiously and pray you get some nice ganks from the jungler. Also, be sure to place turrets far apart from eachother(while not TOO far apart), just enough for his Malefic Visions to not jump between them. Also, he will use Malefic Visions to pry you away from your towers. You really have no choice but to run from your towers, going against the number one rule as Heim. If he lands his ulti, Nether Grasp, you're dead.
Annie, Hard
Annie is a very challenging champion to fight, for a lot of mids. While she is not as powerful against Heimerdinger as others, she will still rape you if you step away from your towers with her Pyromania. A nice way to counter this is to pick up an early Quicksilver Sash.
LeBlanc, Medium
This will be an easy lane if you know what to do. If you just go in and spam abilities trying to kill LeBlanc, you're screwed. Basically, place your turrets spaced apart a bit, just enough so her Distortion cannot hit both of them. If you see her using Distortion, throw a ch-1 concussion grenade where you predict she will land. If you can stun her, shoot your Hextech Micro-Rockets, place H-28G Evolution Turret behind her and pop your UPGRADE!!!. If you can accomplish this whilst she is stunned, you should have an easy kill. Like Katarina, though, hope she doesn't snowball off of kills from other lanes.
Heimerdinger, Medium
Facing an enemy Heimerdinger is very rare. However, it does happen. In this case, I max Hextech Micro-Rockets early to poke him down. Ganks from a jungler always help. When the jungler ganks, be sure to have them Smite the enemy H-28G Evolution Turret.
Kassadin, Easy
Kassadin can be a very easy lane for Heimerdinger. Although it may be impossible to kill him(if he is smart) due to his Riftwalk, you should be able to completely and utterly out farm him and crush their whole team late. Since you will be basically free-farming, you should easily get 5/6 minions per wave.
Katarina, Very Easy
IMHO, Katarina is the easiest match up for Heimerdinger. If she uses Shunpo on you, stun her and watch your turrets rape her. If she uses Death Lotus, just throw a ch-1 concussion grenade to cancel it out. Basically, this should be an EASY win for you. Just call your mia's and hope she doesn't feed on the other lanes.