You know I've given it some thought and when it comes to assassination some sort of venomous snake is considered a pretty good morph right? But I'd go for something spookier.
I'd be a female Black Widow spider. See she's small enough to get in and out unnoticed, can cause severe pain to her victim and, should the bite be delivered to the right place, the chance of fatality jumps, what's more who the heck isn't scared to death when they see a Black Widow crawling up their arm? While its true you couldn't cover very much ground and are much easier to kill if your target is indoors a spider is less out of place than, say, a rattler.
Now if Ax had been a Black Widow when he bit Visser Three he would have been small enough to just keep biting him until the Andalite host body died . . . of course there's the whole "how would he get onto the Visser" question, but bare in mind, them spiders can make parachute things out of their silk and fly around, scary little buggers, so Ax flies onto Visser Three, bites him, then Visser Three gets super powers.
. . . no wait . . . well, never mind, the point is a Black Widow would be an awesome morph.
