-TMP and occasionally whatever shotgun I have against the El Gigantes..
-TMP and handgun against Mendez, as well as Grenades...you can't really get close enough (without him belting you anyway) for the shotgun or riot gun to be very effective.
-In the two Garradors room, I use the rocket launcher you pick up in Ch. 3-3 and shoot it between the two Garradors...on normal, the unarmoured one will be killed and armoured one will only take a couple rifle shots to his Plaga to be killed. On professional, neither of them die but both will be badly damaged and only take 4 or so shots each to the Plaga to be killed.
-Verdugo..rocket launcher bought from Merchant in the spike pit, after freezing him of course. Even with freezing him with the LN2 first, you just use way too much ammo with the normal guns (even the Butterfly) to justify the waste!
-Salazar...A few Broken Butterfly shots to the swollen eye follwed by a rocket launcher bought from the merchant..on normal this finishes him off, and comes very close to doing so on professional.
-U3...if I can afford it, a rocket launcher...on normal it kills him and in pro leaves him in a near death state.
-Krauser..Broken Butterfly and knives...no point wasting the other ammo with that arm shield of his, and he's very vulnerable to knife attack.
- Saddler...rifle the eyes on his legs, use the crane thing to smash him, and Broken Butterfly and also Striker if I get close enough. And the special launcher obviously, when it is thrown.