@Otter : Your weapon without texture is already very good !
@Sivan : In fact playing Guild Wars 1 , they used some sprites for very far building and other stuff ! Even if bad oriented some times you didn't notice it a lot and approchaing , a smooth alpah transition was made to put some other real polygon LOD !
Some times because there was moutains on the side, you could be far from a building only in some part of the terrain, so they put a sprite when you was far and the orientation was good (even if approximative in some manner) !
Others techniques are real time LOD sprite generation each 10 frames or more you recalculate your very low LOD model and make the sprite of it.
Because when a model is very far it will take lot of time before you move of some degrees around it or lot of time to approcha it ! There was a subject on that in some GameDev article.
But well, you can just make some very very low poly model it will work also