That would depend on the boss fight. For bosses like El Gigante, I'd use the tmp because its rapid fire and you can get more shots in before you need to dodge his attack. However for bosses like Mr Sanchez (chainsaw guy) the shotgun is pretty good. But you have to use your knife for krauser because just one slash of the knife and he will throw a flash grenade. Took me ages to work that out. Hope this helps. 