Pen theft prevention and the most hated smell

At work, I get asked for a pen daily. We should seriously sell pens, or we should offer pens that punish the user for being irresponsible.

If users are too lazy to buy a pen and "just need one for a second" we could ask them what their most hated smell is. Then we'd rummage through the pen drawer and give them the pen that corresponds to their most hated smell (MHS, as we'll call it). That way, up until they return the pen, they will be miserable.

'Can I borrow a pen?'
'Sure. What's your most hated smell?'
'What? I just want a pen.'
'This is important.'
"Fine. Burning tires.'
(The consultant finds the pen labeled 'burning tires' and hands it to the user.)
Simple as that!

I've also debated getting smell pens that only occasionally emit the MHS, so that we'd get to hear people yell things like, 'THIS PEN SMELLS LIKE A WHARF!' or 'AHHHHH FERRET CAGE!'

(dinner.)

My most hated smell is a toss-up between "festering bath mat", "hippie dreadlocks", and "homeless man subway urine." What's yours?