Regarding power sources, here's something pretty hilarious:

http://www.thedonovan.com/archives/laserrifle/TIS1.pdf

It's a design proposal for a laser rifle that would use 740 grams of polonium-210 as a power source. This has some problems, such as:

• Polonium-210 is ridiculously radioactive. It will even degrade any materials close to it, just from nuclear reactions with the high-energy alpha particles it emits.
• The rifle would generate about 100kW of heat at all times, including when not in use.
• That energy is used to heat gas inside a closed container to a temperature of 2200 kelvins, producing a pressure of 270 atmospheres.