I never hear him complaining about the achievements being difficult, he just keeps at it. It's actually quite admirable. My guild has a few overachievers in it. We usually do the best we can to lend them a hand, but they seem to grind endlessly to earn their points.
I don't usually go off in search of achievements, but there's one I just can't seem to get. Since I'm playing Druid it seems appropriate to get the Guardian of Cenarius title/achievement. The problem is not that it's difficult, but since my character was created after WotLK was released, I have no Cenarian Circle rep to speak of. I find it hard to make the time to go back to the old world and grind rep while still working on endgame progression.
What's your elusive achievement?