Modern warfare 2 is present warfare and that's why its in that game and not black ops. They took it away away because this game takes place in the 60s and back than they didn't have the tactical nuke. Yes it does but u need a 250 kill streak to get it with any hand gun 'The Tactical Nuke is an unlockable killstreak reward in Call of Duty: Modern Warfare 2, which takes 25 (24 with Hardline) kills in a row to obtain.' see related link
No it does not have a Tactical Nuke You are thinking about MW2.