- 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).
- Some of the historical source books (GURPS Egypt, GURPS Imperial Rome, etc.) of the 3rd Edition were frequently noted for being excellent introductions to the periods and locations in question. Some of them were listed as recommended reading for college level history courses.
- 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 40,000 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.
- d20 Modern's economic system is extremely abstract due to the sheer complexity of the economic world but interviews and statements by the designers indicate the level of thought and detail that went into its creation. Why does it hurt your Wealth Bonus less to buy a house than other, similarly expensive things? Because the boost in your credit score received by being a homeowner with a mortgage would help you if you needed to take out a loan or apply for a credit card and you could borrow against equity in that house.
- Phil Eklund is an actual rocket scientist. His High Frontier features 12 pages of designer notes explaining how every one of the technologies in the game would work, most of them with citations to the relevant papers. Half a page is also dedicated to documenting the scale used for all the attributes used in the game. An actual excerpt from the appendix:
To avoid the evaporation losses suffered by radiations that use liquid droplets in space, dust radiators use solid dust particles instead. If the particles are electrostatically charged, as in an electrostatic thermal radiator
(ETHER), they are confined by the field lines between a charged generator and its collector. If the spacecraft is charged opposite to the charge on the particles, they execute an elliptical orbit, radiating at 1200 K with a specific area of 71 kg/m^2 and 213 kW_th/m^2. The dust particles are charged to 10^-14 coulombs to inhibit neutralization from the solar wind. Prenger 1982