$ secret_santa.rb billy timmy jimmy molly mary julie anne

secret_santa.rb

#!/usr/bin/env ruby

def pick_one(a)
  a.delete_at(rand(a.size))
end

def pick_one_not(a, s)
  index = rand(a.size)
  return pick_one_not(a, s) if (a[index].eql?(s))   
  a.delete_at(index)
end

givers = []
receivers = []
ARGV.each do |name|
  givers << name
  receivers << name
end

(1..(givers.size)).each do
  giver = pick_one(givers)
  puts "#{giver} -> #{pick_one_not(receivers, giver)}"
end