I think Rask still works to scare me because unlike the Regenarador those parts you blow off still attempt to attack you. And then it's has G's lovely quality of wanting to make more of itself.
Out of the RE games I've played these normal enemies scare me the most.
RE2: Lickers Lickers can hang off of walls and crawl with incredible speed. They can also pester you at a range with their tongues and those claws are looking forward to impaling your skull
RE4: Dr. Salvador / Regenerador This one's a tie because both are very dangerous enemies and they offer two different fears: Salvador will join in other Ganado attacks to claim your life in one hit which I believe is the earliest in any resident evil game an enemy can one shot you. They are also very efficient as they won't scream and laugh manically they will simply cut for your neck when at range. Regenerador while they only attack you most of the time solo they rapidly heal off hits to keep advancing forward and can extend their limbs to grab you. Even when you think you're safe by removing their legs they pursue you with greater speed and can leap towards your neck while on the ground.
RE5: Alligators Yeah sad that it's not even a BOW but maybe besides Reapers the enemies are the same from previous games.
RE6: Rasklapanje/Lip Lip introduces Air cotangents
http://www.youtube.com/user/Starsoulklr I'm an Ultra Nerd for Video Games so see what I've got for viewing.