In an local script I have this:
script.Parent.Activated:Connect(function()
local Event = game.ReplicatedStorage.HammerAnimation
Event:FireServer(1441361561)
end)
and in an normal script in the workspace I have this
game.ReplicatedStorage.HammerAnimation.OnServerEvent:Connect(function(player, animationId)
local animation = Instance.new("Animation")
animation.AnimationId = "rbxassetid://" .. animationId
local something = workspace[player.Name].Humanoid:LoadAnimation(animation)
something:Play()
end)
Nothing happens when I activate the tool.

5 comments
Paste the animationId in an animation instance in studio to get the correct assetId..
It still doesn't work
Wait , I just realised... why are you firing animation to the server? Even while FE is on , I think animation plays for the player and can be seen by all others..
Animations HAVE to be done from the CLIENT using a LOCALSCRIPT.
Actually, they can be done just as well as a server script, using the Animator inside the Humanoid. http://wiki.roblox.com/index.php?title=API:Class/Animator . In fact, as for your second script, change line 4 to: local something = player.Character.Humanoid.Animator:LoadAnimation(animation)