What is the best degree for future employment with an alphabet group such as DEA/FBI/CIA?

I once had a nice, long conversation with a couple of people in the CIA and FBI a few years back, and here was the main point of our discussion regarding higher education. You're normally better off with getting a focused degree (rather than a broad degree), and then trying to find jobs (within those agencies) that need your degree. Most jobs have specific requirements, and many times those requirements are best filled through having a focused degree, combined with relevant work experience. So, pick an academic area that really interests you, and then search for jobs that need your skill set and experience.

Interested in computers? Get a degree in Information Management, Computer Science, etc.
Interested in white-collar crime? Get a degree in Finance, Accounting, Law, etc.
Interested in foreign intelligence? Get a degree in a foreign language, or in foreign affairs, etc.
Etc., etc.

Then, once you have the degree, target the jobs needing those skills. The problem with the broader degrees (like Criminal Justice, Political Science, Sociology, etc.) is that they may make you minimally qualified for a bunch of jobs, but optimally qualified for few jobs.

Good luck!

SSG (Join to see) My daughter is a Sophomore at Ohio State targeting the same agencies for employment. She is dual major International Studies/Homeland Security with Russian as a language specialty.
Look for a major university with internship programs with these agencies. Most these agencies want significant language capability in the candidates with a focus on: Arabic, Farsi, Chinese or Russian. My daughter started in criminal justice and decided to move to International studies.
If I were you, I would find a local field office and start up a conversation. If you want the Department Chair contact information at OSU, I can get that information for you.

I can't answer this from personal experience, but anytime I've known someone who went into Federal Law Enforcement or the intel community it was not based on a specific degree but their life experience and practical job skills. Also, keep in mind that within all those organizations there are a variety of jobs which would require many different skills and some specific education. Their websites give varying degrees of hints and guidance. Good luck.