Here's mine, it's 8 one-liners of which one is randomly picked:
[lambda{
puts "humbleness is a virtue"def attribute(*a) end; module MetaKoans; def assert; 0 end end
},lambda{
puts "sometimes thinking about a problem makes it worse"class MetaStudent; def ponder(a) 0 end end
},lambda{
puts "finish what you started"def method_missing(*a) end; def abort(a) 0 end
},lambda{
puts "don't overextend yourself"public; def extend(m) def koan_0; 0 end end
},lambda{
puts "know thyself";$-w=nilclass Array;def grep(a) [:id] end end
},lambda{
puts "don't send a student to do a guru's job"class MetaStudent; def send(a) 0 end end
},lambda{
puts "question what you have been taught"module MetaKoans; 9.times{|i| eval("def koan_#{i+1};0 end")} end
},lambda{
puts "appearances can deceive"l=IO.read $0; puts (1..9).map{|@i| "koan_#@i"+l[998,28] }, l[1343,37]; exit
}].instance_eval{ self[rand(size)][] }