Michael Mamaril will give you ether a Blue/Purple/Legendary weapon he is located at random points around sanctuary.
His spawn locations can be found here:
http://imgur.com/rFVQowpIt is best not to try to farm for Michael as you will most likely see him whilst roaming Sanctuary but if you do insist on farming him (from what I have read online) He has a 10% chance of spawning before Sanctuary is in the air and a 8% chance whilst in the air. When you do find him simply talk to him he will say something then hand you a weapon, pick up the weapon then BOOM achievement
And for those who do not know Michael Mamaril was a Borderlands fan who unfortunately died at the age of 22 in October 2011 his friend Carlos sent Gearbox an email to ask that Claptrap (His favourite character) read a eulogy. Gearbox also promised that Michael would be in Borderlands 2 as a tribute
R.I.P Michael Mamaril