No monster has scared me, not even the Daleks. But, the 1970's Autons were freaky, when they were brought back in 2005 for Ecclestones first episode, they didn't scare me anymore.
I can't really say I've watched old Doctor Who enough to be scared of any of the monsters really. I get why the daleks might have been scary years ago, but they aren't now. I think the idea of the cybermen is more sinister than the daleks, because they are basically modified people, but I don't think they are scary as such.
The Kandyman gave me the creeps a bit, mainly because of the similarity to Bertie Bassett.
One thing from modern Doctor Who that did make me go 'ugh!' was when that bloke became an Ood right in front of us. I'd just finished eating when he started peeling the top of his head off!