Plenty of orifices that you could place said pen in before you leave

dip them all in the hottest hot sauce you can find

you get this really disgusting tasting nail polish to stop children (and old people) from biting their nails, I suggest you find some of that and paint the top of your pens with them.

Take them to the bathroom and insert somewhere. Then return them to your desk.

Piss on them!

Take them to the bathroom and insert somewhere. Then return them to your desk. .. yes do that, hahaha

i'd go with that nail biting stuff i know people who used it to stop biting their finger nails and i know for sure it'll stop some one from chewing your caps

Bitteryuck – anti-chew spray for pets. the worst taste for something oderless

Bitter orange for pets! Just make sure you don't accidentally touch it and then put your fingers near your mouth. It is AWFUL!

garlic nail polish.. just awful

There’s stuff used for horses to keep them from biting in their stalls. It’s called “bitter apple” and it’s damn near industrial strength

Post a sign asking if anyone knows who's been chewing on your torchecul. (look it up)

ipecac

Maybe it is the hot girl in the next cubicle.. wouldn't stick in an oriface just yet. Maybe she wants to get caught. Camera! Then decide what to do!

Any good liquid laxatives? I know Phenolphthalein works with just a few drops…