One way to try to get the journalist to read beyond the headline/subject is the EMBARGOED tag:
Although it does sound somewhat pompous, and can backfire if it's not a story worth breaking an embargo for.
Likewise a subject line prefaced by BREAKING NEWS:
As you can see, MySpace's PR seems to think anything to do with their client is BREAKING NEWS, and deserves CAPS all the way.
Both of these are in danger of Cry Wolf Syndrome. Use them too many times and they wear out.
Another, better way to get your press release read than to send it and then recall it:
I have no idea whether these were all intentional but they certainly had me trawling through my trash for the originals. The fact that no explanation is given for the recall just makes it more intriguing.
This reminds me of an ex-colleague who used to put tiny mistakes in his Reuters features so they'd have to be corrected and run again. Doubled his chances of getting them in print.
Of course, overused, both endanger the credibility of the author: the journalist looking like an error-prone hack, the PR flak looking like someone who says something and then promptly takes it back.