That depends in your motivation really. Each of the things you listed requires some knowledge of one of the various areas of the physical sciences. But each one will require more knowledge in a specific area.
For example, Planet Destroying Lasers: this would obviously require a background in physics. However it will also be a great engineering feat, both electrical and mechanical. It will probably involve some chemistry as well (what is your laser going to be made of? what is your lasing material?) However you can get by with only a working knowledge in some of these areas, but no doubt you will need to be an expert in Physics to pull it off.
Tasty Breakfast foods, in this case you need a great knowledge of chemistry, but to say you won't need physics... well that's just plain wrong. You can't very well know how to build your tasty molecules without understanding the physics behind the interactions that lead up to it. Of course you won't need to be a physicist persay to understand these things, but you need the background none the less.
Teleportation: Again physics is key. Though if you plan on sending living things, then you will certainly need knowledge in biology, otherwise how will you know how to put the creature back together on the other end of y our teleportation device? How would you even know if you did it wrong if you didn't know what was the right assembly in the first place?
Monsters from dead body parts/genetic engineering/etc...: These involve all the various areas listed so far, and probably many more!
The point is, you have to find what makes you tick (maybe literally if that be the case...) and work off that. I love flavor chemistry but I am a physicist and have a very limited working knowledge of organic chemistry. I couldn't develop a flavor molecule to save my life. But alas I love physics and that's what I choose to do, but my knowledge (however limited) of organic chemistry has come up in my work several times. Designing Dye lasers for example requires enough knowledge of the chemistry behind the molecules being used to determine what solvents will give the best lasing action, or what trasitions within the molecule are actually good for lasing.
So find what you love and go for that, if you are unsure you just need to get some more exposure. Most US colleges don't require you to stick with a major if you don't like it, so sample around and take classes in the areas you are interested into find the topic that makes you giddy.