All the mass would be converted into energy, even more energy generated than in nuclear reactions. All the world's particle accelerators together only make about a billionth of a gram of antimatter per year. Solar sails would work well in the solar system and maybe even in interstellar space. Photons from the Sun would hit the sail, transfer momentum, and away you go. Sail would need to be huge, many kilometers across.
Ramjets are a favorite of sci-fi authors.
Scoop up material as you travel, use it for fuel. Cuts down on the weight of the vehicle, so that it can travel faster, nearly the speed of light. One new addition is the ion drive Deep Space 1 was launched in 1998 and uses this technology. The spacecraft slowly accelerates so that the longer it travels, the faster it goes. Interstellar travel is hard.