One good method of dealing with guilt-trippers and manipulators that I discovered recently is the following. Say, the manipulator starts telling you in a tragic voice how “once I’m dead, you will feel sorry that you refused to do this little thing for me.” As soon as s/he does that, start laughing as loudly as you can, saying, “You are too funny! I love it how you always make me laugh. Wow, you are such a hoot!”
The important thing is not to allow wailing, weeping, and guilt-tripping to distract you from the selected course of action. Remember that all of these sighs, tears and fake depressions are nothing but the manipulator’s tool in the service of enslaving you. The moment s/he sees that this particular mechanism produces no result, the manipulator will lay it aside.