In the semi-realistic space combat I design, the following rock-paper-scissors relation holds:
- lasers beat rockets
- rockets beat armor
- armor beats lasers
The level of technology is not too futuristic: no antimatter, no space elevators, no teleportation. Distances are long enough to make direct usage of lasers problematic due to the light scattering and diffraction, but short enough to use rockets with explosive payloads.
All is merry and well here until unguided weaponry arrives. Bullet-like things are not ruining anything as they are either too slow or too fast.
Too slow is self-explanatory. A spaceship is likely to perform defensive maneuvers by firing engines at random, so nothing can predict where it would be in time the bullet is supposed to hit it.
Too fast makes a bullet glow with heat. It heats by hitting trace molecules of gas in space. After all, it is not that empty. A bullet is destined to evaporate or to be picked off by a point defense system.
The ones that are ruining space combat are unguided bombs and mines. Slow-moving nukes that will blow up or melt everything too close to them. You can't avoid mines, because they are invisible. The absence of significant heat signatures makes them impossible to detect.
How feasible it is to use nukes as a spotting mechanism? Blow one in front of you, being at a safe distance, of course, for it to heat everything around it, opening a window to detect otherwise invisible objects.
Something like a flash is used in cameras or a powerful radar impulse.
P.S. Let's pretend for a while that it is possible to mine in such a clever way that there are reasonable chances that a mine will find its target if unnoticed.
EDIT: Maybe the nuke might be not a conventional one, but rather some variation of enhanced radiation weapon, but with focus on alpha particles for increased absorption and thus heating.