Tsk, tsk,tsk...don't use a pen. Yuk!
Use the end of a piece of onboard cutlery, like a spoon, fork, or now (thank you UA!) a knife. Pre-sanitize the dime with scalding water from the coffee brewer.
If you hadn't figured it out, the dime spreads the force across the cork, preventing the cutlery from splitting the cork and leaving bits in the wine.
We will quiz the crew on the MLK DO flights, so make sure this gets around before then - they may get a prize!
Now that the TSA allows corkscrews through security have any of you FAs considered adding a small one to your flight bag?