Similar to other fuel suggestions, not much new. Slightly off the track of discussion.
Hydrogen-fusion: plentiful and cheap, renewable, and compact enough to not be too annoying.
But takes enough storage to make you stop once in a while and visit home or a shop.
Can mine a little and temporarily turn your ship into a slow/immobile, and vulnerable, "capital ship" (regardless of size) to operate a factory and process the renewable nebula/planet/asteroid material, if you're desperate. Hard to be stranded, especially with backup power from other systems.
Antimatter/???: expensive, very compact. Equal/slight bonus to power.
Solar: Has to go on the outside(pending implementation of inside/outside), cheap, light.
Zero-point: Softcap, boxdims, know and love it, may take a powergen/softcap nerf.
(Maybe expensive and/or heavy. If not expensive or heavy, can be the same block as hydrogen and antimatter reactors. Otherwise, it shares the block with antimatter. Or, antimatter and hydrogen are the same block and zero-point remains separate. Hydrogen should be the "standard, middle option", and thus should not be expensive or heavy. But we should compress the blocks down as much as possible, make it simple and easy.)