I am an "IT Guy" and a USAF veteran.
I started RPGs with the D&D "Rules Cyclopedia," and developed from there: D&D, AD&D (1st and 2nd Ed, now in 5th Playtest), d6 Star Wars, Shadowrun (2-3rd Ed), WoD (Old and New), Twilight 2000 (1st, 2nd, and 2013), Hero System, even BESM and FATE. Probably several forgotten others.
I enjoy using abstraction, but appreciate getting into the nitty-gritty when necessary as well (it often isn't).