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.

SSG (Join to see) it really depends on your chosen field of employment.
For example if you decide on a career in IT, certifications are more favored than degrees, especially in the government sector.
If in law enforcement or intelligence, I would say criminal justice or political science.

Mine was chemistry and worked great as an entry level degree for DEA

My response might sound a tad boring but in reality, it is not. Accounting is a very sought after discipline especially forensic accounting. Why? Based off of the "follow the money" paradigm. Go for a Masters in accounting with perhaps a Bachelors in either accounting or finance then add a CPA with a Certified Financial Forensics (CFF) credential along the way and the alphabet soup agencies will be beating down your door. I hope this helps.

Well, that probably depends on which alphabet agency, and what your skill set is. Years ago the FBI had lots of accountants, and hacker types getting hired. There are lots of agencies out there to choose from. What do you enjoy? How do you want to spend your time? It's probably less about the degree, and more about you, and finding the right place for you to fit in. You might have your heart set on the idea of operations, speaking Arabic, and sleeping in the sand. The reality might be that you prefer quiet evenings by the fire reading a Tom Clancy novel, and working a nice federal job somewhere people are not trying to shoot you. I'd say do some soul searching, and pick the degree that best matches you as a person. Then get hired at the agency that is a really good fit for who you are as a person.

I will throw my two cents worth in. Generally speaking, the "requirements change constantly so there isn't a specific degree to being working on". anecdote is true because the agencies have certain numbers of personnel with specific specialties in certain allocated positions. Not unlike the military, when they suffer retirements or employment losses of these people moving on to somewhere else, they need to fill those specific needs left vacant. Sometimes they need more people in Forensic Accounting to "follow the money" so to speak or they may need people with specialized knowledge in computer systems and informational technology. Overall, from my experience with working with DEA and FBI Agents was that many had Criminal Justice Degrees and were prior military. That was predominant with the Agents I worked with over the past 25 years anyhow. Personally, I completed a Bachelor's Degree in Criminal Justice with a minor in Psychology and later completed a Master's Degree in Management with a Specialization in Organizational Management that served me well and still does.
I would recommend a Major in Criminal Justice and Minor in something like Computer Sciences or Accounting. That way you are making yourself more marketable to the agencies than just relying solely on your Major in a degree. Hope that helps! Good luck to you!

Anything Cybersecurity related or certs that match DoD directive 8570. ...I tried posting earlier so if this is a dupe, apologies.
Don't download ANYTHING illegally, oddly, some agencies view this worse than drug use.
Most of the job openings have what degrees they're looking for: http://www.intelligence.gov/how-to-apply/career-search.html

Forensic psychology, forensic accounting, economics, criminal justice, and law degrees are just a few that would be attractive. I would look for a specific agency and a specific role within that agency you would like to pursue and figure out an educational background which would match up best for the role. While there might not be specific degree requirements, you should be able to ascertain a general idea of what would be acceptable when you eventually apply.