There's also Blackwater USA (now Academi)
Not exactly. Blackwater was never one company. The oldest part of the company was what is now Academi Training Center, which Prince started as a training place for east coast seals. They made targets under another company, their contractors were hired through yet another company, and there were at least two more (the last time I was there their APC was on display and I believe that was another company). I believe Academi does still have "official" (i.e., approved and on record) status in some regions for high risk security jobs, but
1) Almost all of their contractors also work for other companies, because they're almost all 1 person companies like Black Ice Security Services
and
2) They no longer have the share of the international private security sector they once did. Currently, the DOD employs Ares Group, SekTek, American Security Programs, Dyncorp, Global Integrated Security, Global Strategies Group, Aegis Group, L-3 National Security Solutions, Kroll, Triple Canopy, and finally a lot of "Miscellaneous Foreign Contractors" who all somehow have companies without names but are hired for things like "Support-Professional-Other" and all share the same address (2011 Crystal Dr. ste 911, Arlington VA).
BAE, Halliburton, Lockheed Martin, and those guys are very different. Not only do they mostly manufacture, they're also linked into universities and interdisciplinary research groups like the Johns Hopkins Applied Physics Lab. Often enough, the same people who are behind your smartphones, navigation systems, computers, etc., are also developing better and better learning algorithms for unmanned aircraft, are in nanotechnology and materials sciences making newer more sophisticated armor, or lighter small arms, or the rifle that''s going to replace the m16/m4 system (and has been "going to replace" it for a decade or more), etc. Oh, and they're also the PhDs behind detection devices used in airports or other large public areas. A major problem that was only fairly recently addressed was that so many current detection devices didn't work for the IEDs that were used in the US and abroad. Virtually all high explosives (nitroglycerin, RDX, Ammonium Nitrate, TNT, HMX, PETN, etc.) share one essential ingrediant: nitric acid. In fact, they all rely on a triple nitration process. So that's what everything from sensors to dogs were able to detect.
Peroxide based HEs don't use Nitric acid. Of course, they're extremely unstable and they break down quickly (which is why no military uses them), but the reason you can't carry liquids onto a plane isn't just thanks to that guy who was caught trying to make a bomb on the plane. It's also because of he was trying to use a peroxide based explosive. But once again, the same people who manufacture arms, military aircraft, etc., are the ones who funded and/or developed things like portable sensing equipment for this class of explosives so that they can be detected.
Halliburton, WalMart, and their environmental and human rights impacts felt around the globe. People don't have to be customers of these companies to be highly negatively impacted by these companies when they are given free reign to run business as they see fit.
There's also the fact that it's hard to know whether or not you are a customer of many of these companies, because unless you have access to Mergent, LexisNexis, or some similar company database chances are you'll have a pretty difficult time trying to track down who owns what and how they're connected to products x, y, and z via grants to labs a, b, & c.
But I'm pretty sure it's all owned by Google and iCult (apple).