[Fixed it by myself]
Tried this, works sometimes, sometimes fails..
local Difficulties = {"Hard","Easy","Normal"} table.sort(Difficulties, function(a,b) return math.random() > 0.5 end) print(table.concat(Difficulties, ' '))
Error: 13:17:48.509 - Workspace.Script:5: invalid value (nil) at index 1 in table for 'concat'
Why not grab a random value from the table?
Difficulties[math.random(1, #Difficulties)]
Also, see http://wiki.roblox.com/index.php?title=Random_numbers#math.randomseed.