[Suicide Junkie]

There is no way to save to detonator ship.

If you time it right, though, you could kill many hundreds of enemy warships.

I would say a black hole would be most effective if you want to just defend. That way the enemy's next wave will have to slog through the hole to get you (unless they can and do open up new warppoints)

A simple sunbuster is good if you plan to mount an immediate counter attack.