Call of Duty: Black Ops
In Call of Duty: Black Ops, the B-52 is used extensively by the USAF in Vietnam as a carpet bomber, where several can be seen at the end of the mission "S.O.G.", bombing the NVA below. In multiplayer, the aircraft drops the killstreak Rolling Thunder.
Call of Duty: Modern Warfare 3
The B-52 can be seen in mission "Iron Lady". If using noclip, it is possible to see that its model is not very detailed.
Call of Duty: Ghosts