I have been developing this rule for use in the Star Blazers Universe, but it would work with some other settings as well.  Here it is:

When two opposing ships end up in the same hex, they are not automatically seperated.  Instead, both players must decide whether they want to attempt to ram the enemy ship.  If both players agree, than ramming happens instantly.  If one player does not want to ram, but the other one does, the one who wants to ram must roll a 4 or higher for the attempt to suceed.  Also, two ships in adjacent hexes could try to ram, but both players would have to agree and a die roll would have to be made for this to happen.

There are two types of ramming: Suicide and Partial.  In Suicide Ramming, twice the current hull rating of each ship is subtracted from the hull rating of the other, likely resulting in the destruction of both vessels.  In Partial Ramming, one half (rounded up) of the current hull rating of each ship is subtracted from the hull rating of the other, and both ships may transfer as many marines as they want to the other ship.

If two players disagree as to which type of ramming they want to attempt, a coin flip is required to determine which happens.  Note that if a player tried to avoid ramming, but failed, they have no say in what type of ramming occurs.

What do you guys think?