I was quite appalled to read this headline for a story about an ex-PM of Vietnam:
A Malaysian death wish for ex-PM
This story is among the "Most Viewed" online and has presumably made it to print. You only have to read the lede to realise that what the writer meant was "final request", "last request", or "last wish". None of these death wishes! Here's the dictionary definition of death wish, which has very negative connotations:
death wish n.
1. A desire for self-destruction, often accompanied by feelings of depression, hopelessness, and self-reproach.
2. A suicidal urge that presumably drives certain people to put themselves consistently into dangerous situations.
* death wish. Dictionary.com. The American Heritage® Stedman's Medical Dictionary. Houghton Mifflin Company (accessed: July 28, 2011).
If you want to use an idiom, make sure you know what it really means!