var participants = ["Paul","Matt","Owain","Joe"],results = [];
var hat = _.shuffle(participants);
_.each(participants, function(participant){
  var picked = _.sample(_.without(hat,participant));
  results.push([participant,picked]);
  hat = _.without(hat,picked);

});
console.log(results);
// each participant

if ( participants.length % 2 === false ){
  participants.push("unassigned");

}

var pairs = [];

// Pick n items from array
function pickFromArr(arr, count) {
  var pair = _.sample(arr, count);
  participants = _.filter(arr, function(item){
    return ! _.contains(pair,item);
  });
  return pair;
}

while (participants.length!==0){
  pairs.push(pickFromArr(participants,2));
}
console.log(pairs);