From the very first episode and one of the first things Senjougahara says:
"Don't move.
Oh, my bad.
I mean, you can move if you want, but it'd be very dangerous"
What a way to make an entrance let alone your first impressions don'tcha think?
This next one is more like a sound-file as opposed to a quote, but whenever Araragi's two little sisters scream
"Mou!" at him, it gets me everytime XD