I can't tell you how many cover letters I receive from people who get the title of the job they're applying for wrong.
I know what job they mean, because they've put it in the subject line of the email. But when I open the cover letter, there it is -- a totally different job, presumably one they applied for somewhere else right before sending me this letter. Often it's a job that bears no relation to anything we do.
Not really a turn-on. Even if the rest of the application is great, it's hard to get past a big red flag screaming "no attention to detail."