Add gravity it'll make movement more interesting, planets can be used to sling shot ships, gravity mines could be used to pull enemy missiles of course, hyperspace (assuming that you can fly/fight there) could have gravity currents - implemented as several points of gravity that fluctuate between different min and max pull values in unpredictable ways.
Note: a gravity mine (if strong enough) could even bend a laser in another direction.

ps: depending on how you implement hyperspace or other forms of faster than light travel, you could invent allmost any kind of strange physics.