I used to have an old U lock from Walmart that I lost the key to and tried the pen trick, it was a lot more difficult than that!

Any friends in construction? A gas powered concrete saw works very well.

Just reviving this thread for a bit. There's a frame & components (both wheels are already gone) locked up at my local grocery store and the manager is willing to let me have the remainder of the bike (assuming no one claims it and it's been sitting there for over a week now already). However neither he nor I have actually attempted to break through the Kryptonite KryptoLok STD U-lock yet. Any suggestions on how to best accomplish this? The lock is secured through the top horizontal bar of the rack and through the frame (right now it's sitting next to the headtube).

I'm not sure my car's screw jack will fit in there. Will bolt cutters work? I have a hacksaw but no power tools.

Get a carbide grit hacksaw blade.

Wondering of I can lockpick it? - search on "bump key"
Hack saw. - I've done that with carbide blade, not easy.
Grinder - a quality blade will set you back a bit, but is reusable. Work gloves, goggles and ear muffs are a must.
Locksmith - might be fastest method in your case.