A lot of people dont seem to actually realise this and have simply waved it off as merely an inconvenience, but in Modern Warfare 2, the Thermal Sights dont work on snowy maps. - killjoy131
The thing is, thermal sights should work really well on snowy maps. The view through them should be almost completely dark (cold doesn't show on thermal sights) with people, hot weapons, fires, etc. showing brightly in contrast.
A thermal scope works by detecting the infrared radiation, which is felt as heat, then visually representing the source of the IR radiation, snow is white, therefore, reflects pretty much everything on the electromagnetic spectrum including infrared, although this is probably just the result of it being lazily made.
Also in Modern Warfare 2, on the level "Second Sun" there is no enemy intelligence to gather. This is because the EMP that went off would have destroyed any computers.-TGBA
Black Ops is filled with this. When you escape from Vorkuta in the second level, you use a Model 1887 shotgun on a motorcycle. At first, this can be seen as an homage to Modern Warfare 2's overpowered weapon, a fun action scene, and a Shout-Out to Terminator, but then a few realizations are made: it would be impossible to fire the weapon in such a way, it only holds two bullets and that it is highly unlikely to find that gun in a Russian prison. However, the Olympia is gun that you would find being used by Russians (as it is Russian made, unlike the 1887), and it only holds two bullets at a time. Even on the second level Mason is beginning to hallucinate. He thinks the Olympia is a different gun. -ssguy
To continue this the twist of Reznov being a hallucination was hinted at much earlier. When meeting the Defector in Hue City, you meet Reznov which is later proven to just be another hallucination. However, if you look around, you can see a dead man slumped next to a desk. That's the real defector, but nobody noticed him at the time. Also, no one ever directly talks to Reznov other than you. After any scene where you talk to him, you teammates ask you what the hell you're doing, and quickly get killed afterwards. This could originally be seen as bad writing, and the overuse of deaths as "dramatic twists" which has plagued the series, but there is actually a purpose: they're wondering why you are talking to yourself, and they get killed shortly after so that they never reveal this, thereby keeping the player in the dark. This is helped by the fact that you hallucinate Reznov killing Steiner, when in actuality you kill him; it's possible that your teammates weren't randomly killed by Vietnamese soldiers, but by you under Reznov's influence to keep their mouths shut. On later levels with Reznov, the crosshairs won't change color when you put them at him, you'll be able to shoot through him, and he'll take cover more often and fire less. This isn't just bad programming as most people would assume, but placed there on purpose. There's even a part where you climb a ladder before Reznov, yet he is already at the top first, because he simply does not exist. Sorry about the big spoiler, but there was a lot to write, and it was all relevant and just absolutely genius. -ssguy
Of course, this is all muddied up since there is a secret code in the game which states that Reznov may still be alive. So how much was fake, and how much was real? -ssguy
Just because Reznov's alive doesn't change anything. The last time you actually see Reznov is at the end of the prison break (not counting the flashback later on since that took place before the escape). The other ones were still figments of your imagination.
Somewhat of a subjective one this, but in Wa W Reznov's speech is rather stilted and unusual, with odd turns of phrase. In Black Ops, he starts off much the same in Vorkuta, but after that he seems to drop his odd way of speaking. This is because Mason is hallucinating Reznov and naturally renders his speech as a normal American, dropping Reznov's real mannerisms.