What is faster than "wait()"?

It's the RenderStepped event of the RunService. This event fires every render frame, which is approximately 1/60th of a second. You can use it like a normal event (which will basically behave like a really fast loop, since the event is constantly firing.)

game:GetService("RunService").RenderStepped:connect(function()
    print("Spamming your output...")
end)

Or simply use the wait() method, which will wait for the event to be fired until continuing.

while true do
    print("Spamming your output...")
    game:GetService("RunService").RenderStepped:wait()
end

In a repeat loop, it's the same.

repeat
    print("Spamming your output...")
    game:GetService("RunService").RenderStepped:wait()
until
    condition

This can only be used in a LocalScript.

here are some things faster than wait:

while true do
    print("thing")
    coroutine.yield()
end

runservice.RenderStepped:connect(function()
    print("thing")
end)

runservice.Heartbeat:connect(function()
    print("thing")
end)

local counter = 1
while true do
    print("thing")
    if counter == 2 then
        counter = 1
        coroutine.yield()
    else
        counter = counter + 1
    end
end