A block that uses energy to eliminate all inertia, it would allow for sleeker designs as it eliminates the need for backward facing thrusters but would also be heavy and maybe a little larger than their thruster counterparts.
This could work, but it may be a little overpowered and abuseable.
Perhaps these can be placed on the inside of a craft, with the size of about 2x2 or 3x3, they provide no thrust at all and are there to provide a counter force when stopping, like a gyroscope.
Cr0ssley That's what inertial dampeners are and gyroscopes would be another cool idea.