Which abilities are shared in One For All?

Solution 1:

Skills that work with teammates

• Akali's Twilight Shroud also hides other friendly Akalis.
• Anivia's Frostbite will do double damage to an enemy that is 'chilled' by another friendly Anivia.
• Brand's abilities will all gain their passive effect if a friendly Brand's Immolation is on that enemy.
• Cassiopeia's Twin Fang will be set to a .5 CD if it hits any enemy poisoned by another friendly Cassiopeia (Also goes for Teemo/Singed Poison when not in OFA).
• Darius gains movement speed from his passive for bleeding enemies, no matter which Darius applied the bleeding stacks.
• Diana's Moonlight An allied Diana can use others Diana's Moonlight for her Lunar Rush.
• Draven may catch another friendly(or foe) Draven's Spinning Axe.
• Jarvan IV using friendly Jarvan's Demacian Standard to Dragon Strike towards.
• Jayce's Acceleration Gate will boost the power of all friendly Jayce's Shock Blasts.
• Kennen's Mark of the Storm stacks no matter which Kennen applies them.
• LeBlanc's Sigil of Silence can be procced by friendly LeBlancs (including another LeBlanc's Sigil of Silence).
• Leona can proc friendly Leonas' passive.
• Lux can detonate the passive from any other friendly Lux.
• Maokai's Vengeful Maelstrom 5 of those ulti's will make everybody inside almost unkillable.
• Nocturne's Duskbringer Will increase friendly Nocturne's stats.
• Quinn can proc any friendly Quinn's Harrier
• Syndra can use all friendly Syndra's orbs as if they were her own.
• Twitch's Deadly Venom can stack with other Twitch's Deadly Venom and be procced by a friendly Twitch's Expunge.
• Urgot's Acid Hunter will lock on to a target hit by another Urgot's Noxian Corrosive Charge.
• Varus' Blighted Quiver can stack and be procced by friendly Varus' abilities.
• Vayne can stack on and proc friendly Vayne's Silver Bolts
• Vi can stack on and proc other Vi's Denting Blows
• Zigg's Satchel Charge launches other friendly Ziggs upon detonation.
• Zilean's Time Bomb will explode instantly if another Zilean places a bomb on the same target.
• Zyra can create plants from friendly Zyras' seeds

Skills that do not work with teammates

• Passive auras Buffs like Heimer's passive or Janna's passive don't stack.
• Akali's Mark of the Assassin cannot be triggered by another friendly Akali.
• Katarina's Bouncing Blade Mark cannot be triggered by another friendly Katarina.
• Mordekaisers cannot stack their ultimate. If attempted, the skill does nothing but the cooldown resets.
• Sejuani's Permafrost active doesn't affect enemies with Permafrost from another Sejuani.
• Xerath's Mage Chains Stun cannot be triggered by another friendly Xerath.
• Zac can only pick up his own blobs that drop when using abilities.

Possible Skill Interactions (Untested)

• Ahri's Charm increasing damage of friendly Ahri's.
• Darius' Hemorrhage Increases damage of friendly Darius' Ults.
• Swain's Torment incresing damage dealt by friendly Swains.

• Thresh's The Box damaging and enemy only once no matter how many different Thresh walls they break.

• Vladimir's Hemoplague Either refreshing the duration or stacking for more increased damage.