GURPS is famous for this. Writers efforts to provide accurate stats for the real world lead to pages worth of citations and examples in many 4th Edition books. They also have been known to hire people that know what they're talking about as advisers, altering and scrapping sections of the rules in order to allow better simulation of reality. Notes that appear alongside the official rules often include notes on how to make the game even more realistic, though notes to the effect that using more realistic rules might bog down the game typically accompany them.
This got them in legal jeopardy in 1990, when an over-zealous warrant led to every computer at the firm being confiscated by the Secret Service due to ongoing research at the company for a Cyber Punk genre book. The author had consulted with a few real life hackers, but the book was hardly a 'handbook for computer crime' as one misinformed agent said. It led directly to the creation of the Electronic Frontier Foundation.
Actually, the raid occurred because one of the people working at SJ Games happened to have a pirated phone company book on a machine in his home. The overly-reactive raidand subsequent founding of the EFF did indeed occur; it's just that the manuscript was picked up while the Secret Service was in the building. It didn't help that they wouldn't immediately disclose the reason for the raid, leading those working at the company to the most immediate conclusion (that a sourcebook on hacking had brought down the wrath of some people not known for their affection towards BBS operators).
Ars Magica from Atlas Games has several supplements whose entire purpose is to Show Their Work, most notable for this being Art et Academe. Most of the authors have some qualification in Medieval History or a similar topic.
Warhammer 40000 goes into this at points when they can justify it. For example, Lasguns are only nonrealisticly displayed in art and video games because they would otherwise be really boring. That they make noise and light is generally explained by psychic influences. On the other hand, it might be that 40k really does have Frickin' Laser Beams, and the Mechanicum just doesn't know what they're doing.
