My list;
Houndoom - a howling dog from hell
Cacturne - Imagine yourself, in the middle of the night, being stalked... And then when you turn around, you see a Cucturne, smiling right at you...
Banette - Silent Death? Or something like that...
Glalie - A dark scary face in the caves, staring at you...
Muk - Eh, it's just creepy looking.