41. Snake Can Use The Codec Silently
This might be nitpicking, but I never understood this. Apparently the Codec is implanted near the small bones of Solid Snake's inner-ear, which allows him to listen silently, but how can he respond without making a noise? This is especially problematic in MGS3, when Big Boss is using a regular radio to communicate.
40. Back Of The CD Case (MGS1)
This trick was mind-blowing to me. Basically, Snake needed to get in contact with Meryl, but he didn't know her Codec frequency. He's told that her frequency is on "the back of the CD case". Snake is baffled by this, yet players with a resourceful brain (or an Internet connection) figured out that her frequency is literally listed on the back of the MGS1 game case. Pretty cool, unless you had a pirate copy of the game and your parents didn't have the Internet (a pretty plausible scenario in 1998), in which case you were screwed.
39. Rose & Raiden Met On April 30th, 2007, 218 Years Exactly After Washington's Inauguration (MGS2)
This is more of a fun fact. It's relevant within the atmosphere of the neo-patriotic trappings of MGS2.