Sniper is one of the most lethal carries in the game. Given enough time to farm or if farmed, Sniper can drop an opponent in a matter of seconds. He is the only hero that can out-range a tower. He is thought of by many as an easy-to-play hero, however, as is with all heroes, it is hard to use them to their maximum potential.
Magic Wand - I get this for survivability. If you have a normal side lane, then you should get charges on this regularly, giving you good sustain to keep you farming longer. Feel free to ditch it late game.
Power Treads - Give you some movespeed for your slow self, as well as some survivability.
Shadow Blade - You will find yourself in a situation where an enemy has closed the gap between you and him, meaning that you are in danger. This will allow you to GTFO quick. Also gives nice damage and att spd.
Manta Style - Gives a good amount of all stats, movespeed, attack, att spd, and mirror image. Late game mirror image will help you do a godly amount of damage, as well, it can be used as an escape tactic. Keep in mind your Headshot will proc from these illusions, which is why this is core.
Assault Cuirass - Armor and att spd, for your allies too! Very good item on sniper, I highly recommend it.
Not To Get
Any lifesteal. I used to build it on Sniper, but was taught the error of my ways. You are too damned squishy to even have someone attacking you, so just avoid losing health altogether rather than worrying about regenerating it. It's okay if someone has the passive from Vlads, though.
Refresher Orb... I see too many Snipers in EM games grab this. Your ult is on short CD as it is, and it is used to finish someone off. Just avoid this item.
Some other items I didn't mention are Wraith Band and a Bottle.
Wraith Bands never hurt any agility hero, they give you stats which are always helpful, and some damage with the added agility.
Ring of Aquila can be helpful to build from a Wraith Band, if you are running low on mana.
When playing Sniper, I always keep a TP scroll on me. Before you can afford Shadow Blade, you need something to evade ganks, and TP scroll will also decrease the time between going back to base and returning to lane, meaning more farm.
If I have not stressed how important farm is for Sniper, let me do so now...
YOU NEED FARM!
... lots of it. To be of any use to your team, just farm until it gets to the point where teamfights are happening and the team becomes mobile. While in lane this is your first priority.
While in lane, provided you have enough mana, use Shrapnel on the enemy. It can be used to farm and harass, if you are against melee, try to do both at the same time. Just pay attention to your mana. Keep enough in reserve for one Shrapnel at all times until you have Shadow Blade. Once your Take Aim ability is high enough, don't worry too much about small scale harassing with Shrapnel, just AA them.
Keep on farming. Once a good portion of your core build is finished you will prove to actually be a threat to the enemy team. Push lanes and get kills at this point, but I suggest that you keep farming whenever the team is idle. Don't lollygag and go looking for kills, just get more gold so you can become a real heavy damage dealer.
Have your core completed at this point, with a few or so out for situational items and such, and then the enemy team will start to drop fast (if all goes as planned). Push lanes and get into fights with the enemy, and make sure your positioning is good! If your team is behind you, something is wrong. Should a formidable melee enemy come from who knows what small patch of fog you failed to check, you can be killed quickly, and now the enemy team is favored over you in battle (assuming you are the primary source of damage).
Just be careful at this point in the game. You should have good communication with your team, letting your initiator start the fights, and sit behind your tank. All should go well.
This all said, there are some heroes that benefit you greatly, and others that are undesirable to play against...
Red = tl;dr
When a teamfight starts, you should not be at the head of your group. Make sure you are behind your melee heroes or tanks. This is so important I cannot really stress it enough.
If you are at the head of your group you will die fast.
Depending on the enemy team, your positioning should be different. If they are really heavy on melee, do not sit at max range but move up to where if they tried to run you could still pull off a few AAs on them, because they will usually out-run you.
If their main threats to you are melee, move a little closer to them.
If they have range that will try to focus you, stay at maximum range and hit their range because if they want to shoot back at you they will be forced to move up closer to the rest of your team.
If they have a range that is a threat to you, focus that range down at your maximum distance away.
If the enemy has stealth that you should be cautious of, position yourself closer to your team and be ready to use Shadow Blade to re-position. Do not allow a stealth hero to insta-gib you, because you will more than likely be their main target.
Play cautious against stealth, use shadow blade to escape if they appear behind you.
Save Assassinate for a fleeing enemy. Don't poke with it, even though it is short CD.
Save Assassinate for a fleeing enemy. Dont poke with it, even though it is short CD.
Good placement of Shrapnel can deal tons of damage in a fight, as well as slow to take fleeing enemies down. Try to use it in the rear-portion of the enemy team, to prevent runners and still do good aoe damage.
You do very well with any hero that has any means of stopping the enemies movement, or even slowing it. This gives you more time to let your AA chisel the enemy down.
Notable ones are: Shadow Shaman, Lion, Vengeful Spirit, Crystal Maiden, Tiny.
Enemies you should try to avoid or use greater caution: Lina, Juggernaut, Sven, Lion, Shadow Shaman, Gondar, Riki, Templar Assassin. Anyone with a quick gap-closer and/or high amounts of damage. And stealth. Stealth is just bad to deal with as Sniper.
Thanks to the guide "Kardel Sharpeye, the Dwarven Sniper" on PlayDota.com for a format to use for my guide. Also used several things from their guide as a reference. See: Hero Synergy.
This is the end of my guide! Please ask me any questions via PM or ask in comments, will add a FAQ section to guide if I get any.
Also offer me critique on my writing style or anything having to do with my writing and ability to write a guide! Was I lacking detail? If so, what? If you could help me out here it would be much appreciated.
Might add a general "Sniper Tips" section later on.
Rate and comment! Thanks for reading.