Switching it up somewhat, I started picking up some outstanding fishing achievements, notably The Coin Master and its three sub-achievements. In case you were unaware, the Dalaran fountain is fishable and occasionally rewards you with a coin. Once you collect them all, you get a nice blue coin to flip to your hearts content. It's a pure grind and very random - expect to cast a couple of thousand times to get the achievement. I mostly did this while waiting on a raid to form or Wintergrasp to pop - the fact that it's in Dalaran makes it a fairly easy achievement to give a few minutes to here and there. Each coin has a 0.3 chance of dropping and yes, there can be duplicates. Trying to get them all is an exercise in frustration. Two things to note: Get your fishing skill as high as possible with gear and buffs - the fountains are high level and the last thing you want to be doing is gathering a bunch of junk rather than coins. Also, the gold coins can be thrown back into...
A complete guide to doing every world of warcraft achievement, starting from nothing.