IT ALL DEPENDS WHAT THIS COWORKER HAS DONE. IF HE HAS BROKEN THE LAW, THEN YOU SHOULD.. IF IT'S JUST SOME PETTY OFFICE THING, THEN WORK IT OUT BETWEEN YOU.
Yes. It's the right thing to do, even if it's painful.
Swiss should be capitalized; coworker should not be capitalized.
If a coworker is being electrically shocked, do not touch them, and shut off the power.
Yes it should be hyphenated: co-worker.
you should modify the problem
Don't talk about it.
Ignore it completely
Hiring that coworker
No, do not give a card for the anniversary of the death of a coworker as it's in poor taste. Although many will have fond memories of their coworker and miss them, most would prefer to just move on.
A gift certificate to his or her favorite restaurant or bookstore.
if it doesnt affect you negatively
The coworker is probably joking with you, but there is always the small possibility they are not and the best thing to do is say 'Is that so'; turn around and walk away.