(You see, the < blink > tag doesn't work on IE! Some may see this as a drawback, but I see it as one of IE's redeeming features.)
All you need to do is set the marquee's speed modifier so high that the text just looks like it's blinking. Make sure that you make the width a set number, so that people with different screen resolutions don't see some crazy text that isn't what you saw during testing. (P.S. - make sure that your width is wide enough for all of the text to be read.)
< marquee width=600 loop=-1 > Sample Text < /marquee >
Oh, and make the loop infinite, why don't you.
After you've got the width set to your amount (I don't care what it is), set a really high scrollamount (speed) value (think in hundreds), and fiddle with the number until you can get it to seem "blinky" and not "marquee-y." It depends on the width of your marquee and how much text you put in it -- don't just use my numbers without testing them first.
< marquee width=600 loop=-1 scrollamount=500 > Sample Text < /marquee >
Now you can annoy everyone, not just Firefox and Safari users! :D
Feel free to /msg me if I've bolloxed up the code somehow.