Can hexproof creatures be countered as they are first casted? I ask because {Thrun, the last troll} has hexproof but before that it says he cant be countered. So would a creature like {Dungrove Elder} be countered with say {Cancel}?
Hexproof doesn't come into effect until the creature is on the battlefield. At all other times, it is a "creature spell" and can be targetted.
{thrun, the last troll} can't be countered because the text on the card says so.....the hexproof is not a factor in regards to countering like BlackJester says.