This guide will show you of many kinds of builds Greymane can use in most situations. I will add opinions and such on why I pick these talents later but for now enjoy the builds and see if any of to your liking and see what kind of good match-ups and threats to Greymane are.

Here's a list of heroes that would benefit Greymane a lot in his team.

Uther: He has pretty good burst healing and either heroic ability can help Greymane out. His Divine Shield can protect Greymane from danger while dashing out some damage onto the enemy plus the extra movement speed can prove useful from fleeing if needed or chase the enemy down if you are sure you aren't going to get yourself killed. Divine Storm is also pretty good as it can potentially stun everyone allowing Greymane to rip the enemy team's faces off.

Tyrande: She has very good Ultility as she make an enemy Vulnerable from her trait which Greymane can take good advantage of and her Shadowstalk heroic ability can not only heal her but make him go stealth as well which help position himself or flee if things get too dicey. Tyrande's Lunar Flare ability is also pretty powerful for a stun as well.

Tyrael: He has many things that can help Greymane make sure he can hit his target and survive a bit.
His Rightousness shield ability may be small but it can make a difference and his Smite ability can increase Greymane's movement speed. Both of Tyrael's heroic abilities can be useful for Greymane, Judgment can dive into an enemy and stun it for Greymane to finish off while Sanctification can help keep him alive from the Invulnerability.

Tassadar: In my opinion Tassadar is gonna be Greymane's best friend. The Ultility and Shields from Tassadar is very strong. Tassadar with Leeching Plasma at level 4 and Tooth and Claw for Greymane at level 20 can heal a bunch since his damage comes from Basic Attacks most of the time and his cleave damage from the the level 20 talent counts. Tassadar's Oracle ability is also useful for revealing hidden enemies which can be problem for Greymane as he can get bursted down easily especially from a Nova or Zeratul.

Kerrigan: She is able to pull enemies back towards her then stun them for Greymane to take part of the
action.

E.T.C.: E.T.C. always for every hero makes perfect use for a Mosh Pit and it is no exception for Greymane as he can deal a decent amount of AoE damage. E.T.C. can also increase Greymane's attack speed a bit every time E.T.C. uses an ability and if he picks Groupies at level 13 he can also heal for a decent amount as well.

Arthas: He has decent Crowd Control for Greymane to take Advantage of. Howling Blast can root, Frozen Tempest can slow and so can his Summon Sindragosa heroic ability maybe even root if Arthas builds into it.

Abathur: he is most of the time very strong when paired with any hero with strong Basic Attack damage when he picks Adrenal Overload at level 4 and Hivemind at level 20. There is also some talents worth picking too if Abathur decides to build for teamfights rather than siege.

Brightwing: She's strong not for her healing but for her Ultility. Pixie Dust can give Greymane a decent speed dust as well some Block charges to defend himself a bit and depending Brightwing's talents she make Greymane reduce some Ability damage as well and her Polymorph can be very useful.

Murky: Just Octograb alone is enough to have Murky a pretty solid hero to be around Greymane and the Slime ability can slow enemies for a decent amount.

Zagara: Devouring Maw can be pretty strong for the entire team and not just Greymane and is worth having around.

Rehgar: He has a pretty decent slow and good healing and either heroic ability can work for Greymane.
Ancestral Healing is never the wrong choice as it's a very strong burst healing ability and Bloodlust can increase Greymane's attack and movement speed by a nice amount and it's perfect when combined with Tassadar if he picked Leeching Plasma at level 4 for additional healing.

Anub'arak: Anub'arak has pretty good mobility as well as Crowd Control. Impale and especially his Cocoon heroic ability can allow Greymane to position himself and finish the enemy off.

Jaina: She has insane burst damage and can slow enemies for a decent amount and if needed for a long time
which can allow Greymane to use the Executioner talent at level 16 for even more damage.

Thrall: Feral Spirit makes for a decent root for Greymane to take advantage of us and while Earthquake is a more situational heroic ability it can be easier to use for Greymane than it is for The Sundering as it one the slow from the Earthquake lasts longer and two doesn't push the enemy away as Greymane can't use his full potential on.

Sylvanas: While in World of Warcraft Sylvanas and Greymane are partically mortal enemies but in the Nexus I believe they work well together. Sylvanas alone has pretty strong pushing capabilities and her Wailing Arrow heroic ability can keep the enemy from bursting down Greymane and at level 13 Overwhelming Affliction and Cold Embrace at level 16 can be very nice from the extra slows and making the entire enemy team vulnerable.

Johanna: All of the Johanna's abilities can be helpful for Greymane. Punish is great for a decent slow, Condemn for pulling enemies back to her and Shield Glare can keep basic attack heroes from dealing damage towards Greymane. Johanna's Blessed Shield heroic ability is also great for stunning heroes allowing Greymane to take some hits in.

The Butcher: He can prove useful as he can charge in and stun an enemy hero and from his [[Lamb to
the Slaughter]] heroic ability it can allow both The Butcher and Greymane to tear an enemy hero enemy apart.

Leoric: The Skeleton King has a fairly strong strong and his Entomb can allow Greymane to kill an enemy hero without worrying about them fleeing.

Lt. Morales: She has one of the most overpowered healing in the game at the moment. Her Stim Drone can make Greymane partically unkillable if you also have a Tassadar on the team with Leeching Plasma from the insane attack speed and movement speed increases.