What OP said: Nuketown was a horrible, horrible, horrible map. Its tiny -- 12 people in that space simply doesn't work, however unlike Shipment or Rust from MW and MW2, it is used as a serious map across most game modes -- even Search and Destroy (which is lunacy on a map where people die so quickly and utterly randomly), and to top it off, it seems to be everyone else's favourite map! What the absolute fuck?
In terms of tactics Nuketown highlights all the things that annoy me most in CoD and seems designed to counter-act my own preferred tactics: despite its small size, the Assault rifle is still king because most of the map is medium-length lines of sight with BASICALLY NO COVER, grenade spam is rife because there is BASICALLY NO COVER, once someone gets a killstreak, even if you have Ghost, you are fucked because there is BASICALLY NO COVER, and you can never really move around because the map is tiny.
I think that map alone would've been enough to make me hate Black Ops, but heh, the rest of the game was so shoddy and half-assed in its aesthetic, writing, graphics, gameplay and literally everything else that it barely even stood out.
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Nobody has said it yet (that I've seen), but I wouldn't be surprised if somebody put Downpour from CoD4 as their worst map: everyone seems to hate that map except me. Its actually my favourite multiplayer map of all time in terms of gameplay because there is room for every single strategy, be it running and gunning, shotgun/smg camping, sniping or a more generic assault rifle build. There is room for the guy with the silenced MP5 and the guy lobbing noobtubes both.