According to multiple sources, the Vaznev-9K is considered the best SMG in Modern Warfare 2. It is described as the most complete SMG in the game, with incredible firepower and mobility. Other SMGs that are highly ranked include the Lachmann Sub, which is tied for the best mobility in the game and has the second-best time to kill when examining ranges under 10 meters, and the Fennec 45, which has the highest fire rate and high mobility and handling. However, the Fennec 45 has dropped down the tier list after multiple nerfs in past patches. Its important to note that the meta for Modern Warfare 2 changes with every update, so the best SMGs may change over time.