I am an IP lawyer (patent attorney) but not in the US, so I cannot speak with absolute authority on this, but I would clarify a few things.
Just because no-one has ever been sued doesn’t mean you’re in the clear. EA won’t be fun to sue even with a good case because it has deep pockets. Smaller fry aren’t fun to sue because they have no money. And as someone mentioned, it is good advertising for the weapons manufacturers so they probably tolerate it for that reason.
I can assure you that just because EA say they’re entitled to use trade marks in that fashion, it does not mean that they are entitled to use trade marks in that fashion. “Fair use for the purpose of entertainment” is not a legally recognised copyright or trade mark exemption.
What you say about patents is a bit unclear. There are essentially three kinds of IP you need to worry about when copying a real world gun: trade marks, designs and copyright. Copyright can exist in design-related aspects but this is quite a grey area and legally difficult, and also not the main concern so I will leave that to one side.
Trade marks cover branding, and can be infringed by use of the trade marks word or sign ‘during the course of trade’. Yes there is a question over whether a gun in a game is trade mark use, and EA is certainly arguing the toss, but I think it is more likely than not to be trade mark use. For example, the doctrine of trade mark dilution may be invoked (essentially alleging damage to a trade mark by association with something unpleasant/unsanctioned - one of the classic cases involved a coke bottle used in a ***** film, and also the Dallas Cowboys sued the makers of Debbie Does Dallas; it’s a wonderful area of law…). So if you use a direct reference to a trade marked name, which may be the maker name (Colt) or the particular brand of gun (Desert Eagle), then you are potentially in legal jeopardy. Will you get sued for it? In truth, probably only if you are medium successful (got enough money to make it worth suing but not enough to put up a big fight) and/or make the trade marked guns look and feel lousy. Who knows, but if you want investors, play it safe.
There are such thing as design patents and registered (also unregistered) designs elsewhere. These cover the shape and appearance of a product. Here is a Colt US design patent that I found with 5 seconds of searching: United States Patent: 10197224
I don’t know how well-protected everyone’s guns are but chances are they are, and you will infringe by reproducing the same design/product. This is an area where copyright can come into play as well so don’t think you’re in the clear just because you can’t find a design registration. Purely functional aspects are not covered by a design, which ties in the patent point I think, but (strictly speaking) the criteria for what is excluded on a design is not the same as the criteria for what can be granted a patent. Basically the functional exemption is a red herring - as noted elsewhere, just vary the design so it will not be perceived as the same. How far should you vary the design? How long is a piece of string, and what is your lawyer’s hourly rate?
Here is some info on copyright fair use for film makers with a US focus (a related field): http://www.blakewang.com/fairuse_lawyer.htm
Here is something on fair use for copyright (also US focus): http://www.inta.org/TrademarkBasics/FactSheets/Pages/FairUse.aspx
I hesitate to say you’re safe in any situation, but I’m a lawyer… but yes, best avoid all trade marks to be safe. There is some grey area (in at least some countries) over using words that identify a product in trade even if not formally registered, but for all I know ‘1911’ may be/can be registered as a trade mark (doesn’t matter that it’s just a number - you can have trade marks for pure colours these days).
I wrote up a more general IP guide relating to games here if it’s of any use: https://forums.unrealengine.com/showthread.php?105306-IP-rights-relating-to-game-development-(a-brief-guide)
I hope that clears things up - good luck!