Clockwerk

Rattletrap the Clockwerk is a melee strength Hero commonly played as an initiator or ganker while inflicting high damage per second. As an initiator, his main purpose is crowd control. However, he also does secondary jobs such as chasing and map control. His abilities are centered around destroying enemies one by one, while still being able to control all other enemies so he goes uninterrupted. He does not deal reliable area damage like most initiators, but still he is capable of doing a surprising and devastating entrance. His job after initiating is to focus on a single, scary enemy hero that the team would loathe such as a carry, after which he will try to take down enemies that are trying to get away. He also has good map control because he can gain sight to any part of the map at will.

Gameplay
His first skill shoots out shrapnel fairly often over 10.5 seconds, dealing good damage and causing mini-stun. It has a very small area of effect and is not effective when multiple targets are near Clockwerk, so it is beneficial to isolate heroes or hunt lone heroes down. If you can consistently hit one enemy hero over the 10.5 seconds, it deals an incredibly high amount of damage. His second skill is Power Cogs, which sucks in units that are close to him and surrounds them with small structures. These structures don't allow anyone to escape and will push back heroes that try to get close to them, which makes it very useful to combo with his first skill. Can also be used to run away or create an artificial wall, but this requires skill on the player's part. His third skill is a global rocket which has a decent area of effect but a slow travel time, so it is difficult to hit from long range. It gives vision wherever it hits and deals some but not a lot of damage, making it effective to scout, harass, or kill a fleeing hero. Clockwerk's ultimate is a very long range hookshot which shoots out very quickly from him to a target position. If the hook collides with an enemy hero or non-neutral creep, he will be pulled to it and stun as well as damage nearby heroes. It is very good for catching heroes that are running away or off guard, but takes positioning and skill to hit.

Source:

Tips

 * Scepter buff is actually extremely useful for Clockwerk.
 * Rattletrap has 2 escape mechanisms, use them to enter fights, as well as getting away from them
 * Battery Assault works as a ministun, and is effective for interrupting channeled spells or teleports.
 * It actually prevents Earthshaker from casting any spells besides his ultimate. If he tries to fissure, he'll be locked in his animation until he cancels it.
 * You get great map control with Rattletraps Rocket Flare due to the vision it provides.
 * You can also utilize the global cast range of Rocket Flare to kill fleeing opponents.
 * Rattletrap is a mortal threat to many heroes. But he gets weaker late game without items. So, farm. Rocket Flare is immensely useful in this regard.
 * You may spam Rocket Flare very early in the game from your fountain to scout for information on which hero is in which lane.
 * Rattletrap synergizes well with high DPS nukers. Power Cogs can isolate a single enemy and set them up for AOE nukes.

Trivia

 * Clockwerk's helmet was added to Team Fortress 2 on the 18th August 2011 as Clockwerk's Helm.
 * One of Clockwerk's death animations is a reference to the movie Terminator 2: Judgment Day.
 * An old competitive strategy that was used in the original Dota was sending a rocket flare over to the enemy fountain, and having Nature's Prophet teleport to the enemy base and snipe the courier. This tactic has long been discontinued due to triggers being implemented to stop it.
 * Clockwerk's line "Some assembly required" is a reference to a song composed by Mike Morasky, under the same name, for another VALVe game, namely Portal 2.