Saw once an Assassin using Frenzy while I was fighting him as Warrior...
Also saw Warriors running around with Firestorm and other Firemagiccrap. And of course the tanking Warriors with Dolyak Signet, Mending etc. Just walk away and watch them trying to follow you, or getting owned by spellcasters from distance.XD
Oh yeah, and that Mesmer that cast Backfire on me (as Warrior), while I only use Warrior skills, except for Mending Touch which I didn't need at that moment.o_O;