A friend of mine and I were once playing Rock Band (don't worry, I will relate this to WoW soon), and he complained that he wasn't doing so well. Granted, he's much better than most players, but he was struggling to play a moderately difficult song on the expert difficulty (the hardest difficulty in the game). He later revealed to me that the reason he was lamenting his "lack" of skill was that he used to be much better -- so much better, in fact, that he once beat the infamous "Through the Fire and Flames" on expert in Guitar Hero III.
For those who don't know, "Through the Fire and Flames" is generally agreed to be the hardest song in any guitar-based rhythm game, demanding complex techniques that no other song in the series requires. In response to this revelation on his part, I said to him, "No matter how bad you may think you are now, beating 'Through the Fire and Flames' gives you the life-long right to retire from the game without losing any of your former glory in the process." And I believe that. No matter how much his skill may atrophy, beating "Through the Fire and Flames" on expert means he will always be worthy of respect in the Guitar Hero/Rock Band community, or at least always worthy of my respect.
This conversation made me wonder; are there any achievements in WoW that bestow similar prestige? In my own mind, anyone who got Grand Marshal/High Warlord under the old PvP system is deserving of this kind of respect. I would also like to think that What a Long, Strange Trip It's Been would carry similar meaning, but that may just be me trying to think that my Violet Proto-Drake is more impressive than it really is. As for Insane in the Membrane, though I've never met anyone who has done it, I imagine that rather than respecting him, I might just think him very worthy of the title.