SS, in realism gameing the value of trajectory for all weapons comes into it's own in that small, long range and/or very heavy calibur weapons with sub-sonic ammunition have very limited ranges (pistols, sniper rifles, shotguns, firing slugs etc.).
Lacking trajectory many realism games and mods just scale damage or an absolute range limit (SOF II does this) which creates an absolute distance beyond which the weapon is not effective which makes game-play very dystopic and difficult as judging an absolute distance in-game is near impossible.
The 'slope' of a trajectory, and various hit effects gives weapons range limitations with a realistic and smooth transition that players can see and learn that also give a realism game designer a tool for giving games a realistic balance.
There 'might' be some value for beam based weapons in non-realism or science fiction games by including what I call 'Displacement Based Weapons'. All real and imagined particle/beam weapons obey the laws of physics and can be refracted, reflected, defracted and even bent. In WFF for example you could provide a player (say an Engineer) with a displacement weapon that had limited energy that was in essence electro/magnetic and would bend all energy based weapons paths... This could either be a carried weapon or some kind of concealed mine for example...
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