First Lines

Recently, I've been reading a blog, kidlit.com, that encouraged an exercise regarding first lines. Essentially, the first line of the book is what determines whether the agent, the publishing house, or even the reader will continue to read our book. Pouring over pages 139-215 make little difference if the first line or the first few lines don't interest the reader to keep going.
On top of that, according to the author of kidlit.com, some first lines are so general or philisophical that they could go anywhere. Not necessarily uninteresting, just uninformative. I believe mine is too general, but need someone to throw ideas off of. If you want to look at the post to which I'm referring, here is the link: http://kidlit.com/2011/07/25/first-lines-part-1/
I propose we do the same exercise here. Post the first line of your book, tell us what genre and whether it's an adult, YA, MG, etc, and the rest of us will give constructive feedback so that the curiousity factor will be piqued for all who read our first lines.
Mine is a YA sci-fi: She covered her mouth to quiet her ragged breathing.