Gonna have to go with the majority on this. Having dislocated my knee on a few occasions i know how painful it is. Watching someone crank on a kneebar or a heel hook makes me feel ill!
I once heard someone ask Xande Ribeiro (who knows more about jiu-jitsu than everyone in this thread put together) what his favorite submission was. You know what he said:
The one that makes them tap.
Apart from being totally badass, I think that people who really understand jiu-jitsu (which I definitely do not presume to) understand that playing favorites is important in the early stages to get used to using submissions that work well with your body type, but it doesn't work so well in the long term.
In the long term, you have your toolbox, and sometimes you need a hammer, and sometimes you need a wrench. Sometimes you get out the armbar, sometimes you get out the kneebar, sometimes the guillotine, etc.
Mastery is always indicated to me by independence from a typical toolbox and traditional positions. That's how I identify it in competition. That's why I see guys like Vinicius Maghalaes (the TUF veteran; though this is almost certainly true of Draculinho as well) and Bill Cooper and Ryan Hall and Cyborg Abreu, the young guys who operate without the presumption of position (and that's not at all a conclusive list, but guys in which I've found the feature most prominent in watching recent videos) and think "Those guys are masters."