This is probably the most achievements I have ever achieved at the same time:

Finished my last Valiant Charge for Darnassus and got [Champion of Darnassus] as well as [Exalted Champion of Darnassus] (because I was already Exalted with them beforehand).

Those two achievements also finished [Exalted Champion of the Alliance] and [Champion of the Alliance]. And then finally I got [Exalted Argent Champion of the Alliance].

Thats 5 achievements and 2 titles!

Next goal.. getting all the tournament mounts