Zeus

Zeus the Lord of Heaven is a ranged intelligence Hero who functions almost solely as a nuker. He is usually played as a semi-carry ganker type hero, who instead of utilizing disables, focuses solely on delivering tremendous amounts of magical damage to his foes. With the high cast range and low cooldown on his spells, he is able to deliver the most superb and consistent magical damage of any hero in the game. Arc Lightning is a highly spammable nuke that creates a stream of lightning that bounces between enemy foes (up to fifteen times at max level), dealing minor damage. Lightning Bolt is more focused, dealing heavy damage to a single target, also on a very low cooldown. Static Field is a potent passive ability that allows Zeus's magical damage to scale into late game, dealing damage to all enemies within a decent AoE equal to a certain percentage of nearby targets' health whenever he casts a spell. Finally, his ultimate Thundergod's Wrath allows him to strike all enemy heroes with a bolt of lightning, no matter their position, inflicting heavy damage. It can be used for multiple purposes: to finish off low-health enemy heroes limping away, to soften up the entire enemy team during a teamfight, or even to scout out the enemy's position. With the ability to strike down enemies both near and afar, the Lord of Heaven ensures that nobody can escape his wrath.

Tips
These tips were taken from this guide written by the famous Zeus player Merlini.
 * In the laning phase if you are playing a mid or off lane solo Zeus, Arc Lightning can substitute for your normal attack to get last hits due to its low cool down and long range, helping you stay out of harm's way given that Zeus's own attack animation, damage and range is rather meager early on. An early bottle and/or Arcane Boots help you maintain your mana to get last hits consistently.
 * In most cases Zeus's optimal skill leveling is getting one point in Arc Lightning early on for last hitting/harassing and then maxing out Lightning Bolt and Static Field as they increase your damage output by a great deal. Level your ultimate whenever possible.
 * Always use Lightning Bolt before Arc Lightning so you may not lose your opponent in the fog.
 * Always watch your positioning as Lightning Bolt and Arc Lightning have relatively long ranges, and Thundergod's Wrath has global range. Often, there is no reason to be up close in battle unless you are chasing down heroes; and Zeus' fragility compounds this.
 * When trying to kill low hp heroes (low, but not low enough for Ultimate only) in hard to navigate areas use Thundergod's Wrath to gain vision of your enemy so you can Lightning Bolt them to death.
 * During team fights, use all of Zeus's spells (including his ultimate) as soon as possible to make the best use of his passive. Static Field is based on the percentage of current health, not maximum health, so it will do more damage to heroes at full HP. If you wait for the enemy team's health to go down before using Thundergod's Wrath, then Static Field will not do as much damage as it could have.
 * Remember that Lightning Bolt and Thundergod's Wrath provide true sight. Don't be afraid to use your ultimate or cast Lightning Bolt where you think they may be if you believe an invisible enemy may be sneaking up on you or attempting to escape; if an enemy is invisible in a team fight make sure to cast Lightning Bolt before casting Thundergod's Wrath so that the granted true sight allows your ultimate to damage the invisible target.
 * Thundergod's Wrath can have a good synergy with Bloodseeker's Thirst, since it reveal any heroes that has a low health, so Zeus will simply ulti them to get a kill(s).
 * While skipping most of your core items to get Aghanim's Scepter and earlier is a good idea to deal a lot of damage in a short time, it has many downsides. First of all, it will use most (if not all) of your mana, making you really weak and not very useful for a good amount of time. Second, if you don't have items which can increase your mana pool enough to cast your combo (Shiva's Guard, Rod of Atos, Bloodstone, Scythe of Vyse...) you may find yourself without mana even after using your Refresher Orb. Third, you will lack a very needed HP boost or an escape mechanism; this means that you'll be rather squishy and a lot of Heroes could kill you with just a stun and some damage. Fourth, you will probably kill a lot of Heroes, but your carry should do that. Zeus scales well into the late game thanks to his passive ability, but carries are far more useful than Zeus at dealing a reliable amount of damage in the late game. You shouldn't be killing anymore.
 * Thundergod's Wrath should only be used to acquire a kill if your carry is unable to attain it himself. In most encounters, it should be used early in the fight to make things easier for one's team.
 * In late game, Refresher Orb is a better item than scepter as it will allow Zeus to use his spells more often, which owing to his scaling passive is more important than stronger ultimate damage. Using your three spells with a scepter in late game will deal less damage than using your three spells, then refreshing them and using them again. However, Refresher Orb provides you with no survivability, so if you need to be more tanky and durable Aghanim's Scepter is the best choice, since it gives both health and Strength, as well as a boost to other useful attributes. Furthermore, using a Refresher Orb will drain a lot of mana, making you unable to cast your abilities if used carelessly.
 * Because Lightning Bolt offers 4.5 seconds of true sight and flying vision, you can cast it on the ground near cliff-sides or other popular warding areas to check for wards or de-ward without actually purchasing sentry wards.
 * Considering the 25% magic resistance most heroes have by default, effectively deals 168.75/262.5/356.25 (330/405/480*) damage, provided they have no other source of magic damage reduction.
 * Be careful to not kill steal with your ultimate especially from a carry in your team.

Trivia

 * Zeus is based on the Greek mythological god of the same name.
 * As suggested by the game's files, Zeus's name was, at one time, Zuus. The reason why is unknown.
 * Zeus' alternate/fun name in DotA was "Merlini", a tribute to a professional DotA player.
 * Zeus' title in DotA was "Lord of Olympus".
 * Static Field is most likely a reference to the Sorceress' skill of the same name in Diablo II. In Diablo II, the spell also reduced enemies' HP by a percentage within a short radius.
 * Zeus' respawn line zuus respawn 07.mp3 "To err is human. To respawn, divine." is a reference to Alexander Pope, whose quote is "To err is human; to forgive, divine."
 * Zeus' rival line towards, Zuus rival 03.mp3 " Keep in mind, Chen, Godliness is next to deadliness." is a reference to an old and well-known saying "Cleanliness is next to godliness."