Because a number of accidents have occurred when a climber was lowered or rappelled off the end of a rope, it is wise to tie a stopper knot in the end(s) of the rope. My question is what stopper knot do you prefer and why?
It seems to me that the desirable features of a stopper knot are that it should be secure as well as quick and easy to tie. According to animatedknots.com, a figure eight can work free (though I would have thought that with sufficient tail, this would not be a problem).
Though not strictly necessary, if you're aware of any empirical tests comparing the effectiveness of different stopper knots, that would be great. I would also be interested in hearing about any accidents in which failure of a stopper knot (e.g. rolling off the end of the rope due to poor knot choice) was a factor.
I personally always use a barrel knot (triple overhand) with 12-18" of tail but some of my climbing partners have different preferences so I am interested in knowing how much difference the choice of stopper knot makes. In particular, are some stopper knots dangerous to use? I would imagine that a single overhand could be a risky choice (particularly with a short tail).