Heather Krasna, MS
I know many folks who, in this economy, apply for jobs they aren't really sure they want, just because they need to get something. Pretending you're excited about a job that's not a perfect fit isn't easy, and I think most recruiters can easily tell when someone's faking their enthusiasm.
That said, I always tell my students/job-seeking clients that, if they can summon enough sincere enthusiasm, they should try to end the interview by looking the interviewer straight in the eye and saying, in their own words, "I just want you to know this is my dream job." Or "I just want you to know this would be a perfect job for me, and I'm very excited about it." You can get an offer without saying this if you are much more qualified for a job than the competition, but if you are competing against another equally qualified applicant, the employer will choose the applicant who seems most excited about the job.