I like a cover letter. Not to get my ass kissed, but so I can see you draw the lines between your work experience and the job posting. My field is niche enough that there are few applicants with directly related experience, but there are many ways to gain the basic skills required. I can make all sorts of inferences based on a resume, but I don't want to guess when choosing who to interview. Just tell me how you match up and what you think you'll bring to the table. This helps me separate people who are applying for any job they can vs those who know (at least kind of) what they're getting into.