She also bakes cookies!
EverydaySuperGoddess: Muscle? Bah. I’m a mom. I can crush souls with a look.

Get ready for a tongue lashing!
Amber…bamberboo: Most of my muscles are very unintimidating so I'll go with... My tongue. When I unsheath it, things can get nasty.
Colin: My tongue.
Krisco: Definitely my tongue. I can eviscerate stupid and annoying people at fifty paces. (And by “stupid”, of course, I mean people who don’t see the obvious brilliance of my particular ideas. Not any kind of mental slowness. Although that might help if you want to agree with me all the time.) The rest of me is pretty wimpy.
hadashi: my tongue. i will verbally back you into a corner and then skewer you like a shishkabob. take that!
mazeway: Ah, my tongue of course. I'm soft of ab, but sharp of tongue.

Oh, reeeeeeeaaaaally?
Dishgirl: My eyebrows, of course!
Busy Mom: Left frontalis (so I can raise one eyebrow at them)
Elisa Camahort: My left eyebrow.
Emily G: The one that lifts my eyebrow. I can do the wave with my eyebrows, and we all know that anyone who can do the wave with her eyebrows is DANGEROUS.
Jory: The muscle that makes my left eyebrow go up. It puts people in their place immediately, or it makes them laugh. Not sure how intimidating it is yet.
Sabrina: I guess my eyebrow muscle. When I do that to my husband and give him "the look" he knows he's just done something wrong and he'd better work fast to fix it.

I have no idea what she's talking about, but I like the sound of it.
Ann Douglas: My justice muscle.
Graceful: My sassy pants muscle. I'm only 5'2" so I couldn't be physically aggressive with anyone.

In your face!
Charity: My facial muscles!
Jordana: Whatever muscles are required to give someone "the look".
Sleepless Mama: Usually I just flex my eye and facial muscles. It sends my husband scurrying away.
Tiiana: Actually, you should try flexing a vein in your forehead. That way, if they think you’re about to explode, they’ll bend. Neck ticks also work wonders. Make them think you’re crazy!

The sound and the fury
Sour Duck: I sense another set-up (the obvious answer being "the brain").
However, I'm going with the larynx. (And if you've read some of my comments at other blogs you know I don't necessarily engage the former before the latter.)
Tonya: It certainly wouldn’t be any muscle on my body. I would use my authoritative Major stance and command voice!
Jamie: My vocabularius. What's that you say? It has to be a real muscle? Okay, then, I'd flex my lateral cricoarytenoid and sing something loud.
Pamalamadingdong: My jaw
Baseballmom: My big, huge, buff mouth!

The Gray Matter
la Mala: Is my brain a muscle?
Jen Lawrence: My brain. I'm not being arrogant. I'm just really out of shape post baby #2.
Dawn: The brain – always the brain. Plus, I don’t have any other intimidating muscles. None that are available for the public at least.
Just Dawn: Is my brain a muscle? Being blonde and flexing that muscle is FUN.
It intimidates the hell out of people.
Holli: Many would guess it's my "guns of steel" arms (kidding!!) but anyone with half a brain knows you flex the grey matter when you want to scare the hell out of someone.
Carmen: I would hope, my brain.
Margalit Topaz: My brain. It's by far my best muscle, and my mouth is the perfect instrument for making people melt. I'm pretty intimidating when it's time for bed and I want peace and quiet after a day with kids stuck in the house.
Mindy: My brain. Oh, you don't think so? You want a piece of me?
Clickmom: I'd flex my brain.

Can't we all just get along?
MoMMY: I’d like to say my brain or my sense of humor but sadly they only intimidate me.
DaniGirl: I generally cringe in fear of conflict, so trying to intimidate anybody is a bit of a stretch for me. However, if I had to I could probably talk my way out of a paper bag. So my answer is my tongue muscle, I guess. Somehow, this isn't coming out the way I expected...

Are YOU talking to ME?
Eulallia: Maybe my scary neck muscle with the big vein... I dunno.
Nicole: My left bicep is enormous from packing around a 30 pound toddler.One flex, and the thugs go running.
Lauren: My biceps, I have a surprising amount of definition.
Jenijen: My upper arms always impress. Because I have been carrying a child in them for nine plus years.

Look, people, we're stretching the definition of 'muscle' a bit, but okay.
Justice: My nostrils! :-)
Desperate To Be A Housewife: My finger...namely the middle one.
Allison: my hair, on a good hair day
Tuesday Girl: ????????
Lucinda: Well, I have double-jointed toes and all who've seen me flex them have cowered in my presence…

Oh no she didn't!
Karen: My ass. It's no lie that it's the biggest muscle on the human body -- and, in my case, it's quite possibly the biggest (softest) muscle in the Western Hemisphere. If I catch a glimpse of it in a mirror, I intimidate MYSELF.
Jenny: I'm going to have to go with my butt. Actually, I probably don’t even have to flex it. Its. Just. So. Biiiiiig. Intimidated? Yeah you are.
Susie Sunshine: Usually engaging my mouth muscles in speech does the trick quite nicely, but sometimes my large mom-ass is needed to provide backup.
Beth: Um... Is my smokin' ass a muscle?
Erin: My pectorals, if you could see them.
Meghan: My left bosom. I think wiggling just one would scare them pretty well.