Phantom Lancer

Personally I always look at Earthshaker (his illusions feed the power of Echo Slam), and Medusa, who's ultimate causes 500-1500 damage to illusions and Split Shot lets you clear them out pretty well.

I know it may not be your best option, but I feel that at least an honorable mention should go to Outworld Devourer, as his Arcane Orb deals 400 bonus damage to illusions, plus his ult is an AoE nuke.

I think items that deal area damage like Battlefury and Mjollnir also help in countering PL.

the problem with PL is, that once he has his Heart of Tarrasque, u almost need aoe dmg to clean his illus or to see who is the real one is. Therefore simple aoe dmg spells like Light Strike Array or Dragon Slave are wasted. Therefor i can only agree with all those who mentioned Luna Medusa and Gyrocopter ...all of them have a way of clearing illusion rather fast and without the waste of mana or cooldowns

Thanks for all the great advice. I chose to go with faceless void, who I hadn't played before. I'm doing really well with him and find him an excellent counter to PL as well as many others. I recently had a 36/6/6 game with him against a side with PL.

I like to pick Gyrocopter or Leshrac as a PL counter

I think Kunkka with his Tidebringer and Sven with his Great Cleave are effective counters to Phantom Lancer. The only problem is if these 2 heroes are underfarmed compared to the enemy team's Phantom Lancer, then there's very little that they can do.

PL is a powerful carry, yes. But, as with every carry, he can be countered with the right team and know-how.

Wards/Dust will prevent him from stealthing away, while AoE will reveal which one is the real PL, stuns/silences can prevent him from getting off his actives, and flat, single target damage can drop a phantasm in very few hits.

Good counters would be anyone who can fight illusions. Earthshaker and Gyrocopter being my favorites. Tidehunter can do pretty well, same with Birstleback and Slardar.

Map control can also really hurt him. If the PL thinks he's going to be clever and get a solo kill, but ends up being 5-man smoke ganked, then the only way he'll get away is if:
A) he's fed out the wazoo
B) he's really super clever
C) Know about your wards, and is luring you and your team to a very painful death
D) None of you brought dust *HINT HINT*

Dust is easily countered by diffusal --> doppelwalk.

Wards or a gem are required.