FemShep definitely keeps a gun strapped to her thigh when she wears a dress.
The cocktail dress hugs her body just right, black fabric stretching over her hips as she sits down, crossing her legs and motioning you over.
Of course you take a seat at the edge of her lap, that's commander Shepard. Who could ever refuse Hercules a request? Her hand settles on the small of your back, lower and lower, firmly pulling you higher up her leg, until you're seated on her thighs, closing the distance between you two.
You're unsure if it's really allowed, to just use her steel-like thighs for your pleasure. Hesitantly grinding down, uncertain movements and subtly rocking back and forth. She seems pleased, if that sinful red-painted smile on her face is anything to go by. So you keep going, hips moving bolder and bolder as you ride her thigh—until you feel something solid and cold brush by your most intimate area.
A renegade Shepard would definitely want you to continue still, grind on her strapped pistol, why not? It's fine, just keep going, you were already doing so well. The short hem of her dress still hides just enough of the gun, you can have plausible deniability, claim you never felt it in the first place and seek your relief between her scolding flesh and cold iron. She won't bring it up later, if you won't, your obscene act in a lust-clouded haze... maybe.
You're sent to assassinate her
Sometimes life gets rough, even for assassins! In a moment of weakness you accepted that bounty on Commander Shepard's head that's been posted for an ungodly amount of credits...
Yeah many other mercenaries came before you for her head, and failed, quite embarrassingly. But you're different! See, they failed because they let their ego get the best of them and focus too much on a dramatic entrance. That's just dumb! While you always preferred a mere subtle and direct approach, to get the job done as quickly and cleanly as possible.
Your target is known to frequent nightclubs during her shore leave, all you have to do is doll yourself up and throw yourself at her under the pretence of being drunk, take her to a back-alley to make out, then blow her brains out, and go collect your retirement. In and out, all in a night's work! Bada bing bada boom!
Except your plan derails a bit, when instead of you even getting to make the first move—by bumping into her, spilling your drink on her then apologising profusely—Shepard gets to you first. Intimidating the person on the stool next to you to scurry off with nothing more than a single look, before immediately taking their place, and asking if she can buy you a drink—while actively buying you the said drink before you could answer.
Okay, little strange turn of events, but maybe you're just her type? You can go with the flow, keep up the charade of a starred eye fan who never expected a celebrity to take interest in you! Except she actually seems more interested in talking about you than bragging about her achievements, huh. It's a little tricky having to come up with answers on the spot to her personal questions, traces of truth keep slipping out as you try not to seem suspicious.
She just attentively listens, throwing a flirty remark here and there. And when she coaxes you into the dance floor, you're almost floored by the discovery of how much this real life valkyrie is godawful silly at dancing. It's kind of endearing.
The two of you stumble your way out the back entrance, arms around each other, laughing your hearts out. It's hard to keep track of your mission still in the haze of events, but you sneak a hand around her waist and nudge her towards the wall. She understands your intentions and relaxes her body in your grasp, completely letting you move her around as you wish.
There is a twinge in your heart as you kiss her neck. You try to shake the remorse off but it creeps on you alongside the smell of her perfume, it's intoxicated how her body desperately pressed back into your own.
The idea of walking away crosses your mind for a split second, but you immediately push it down. You can't let your conscience get the better of you now; your heart has long turned into stone. This is merely another job, plus you'll literally be set for life after it. Her eyes are closed, pleasure filled groans filtering through her lips, shiny and plump from all the kisses you drowned her in. This is the prime opportunity to act, your hand moves to your back pocket. Oh she must think you were undoing your belt, for her own hand moves under the split side of her dress... You swallow your dry throat at the idea of her reaching in there to pull her panties down.
Only for a gun to press against your hammering heart. She kisses your lips, the sparks fly, your still warm body makes a thud falling down.