ToME WikiRavenRed: Just a minor idea, partially derived from playing DoomRL.
Would it be possible, or even should it be desirable, that missiles fired at a monster that miss should continue in a straight line through that monster. The chances that they hit a second (or third, or fourth) monster could be limited to perhaps 25% or less of the initial chance to hit to make it more of an effect than a bonus. Piercing shots could remain, but would be applicable AFTER they hit a monster. It's more of an aesthetic thing than anything else, I grant you, but it would add a minor touch of realism to missile effects.
2cworth and counting
ChrisAmes: You'd think that if you missed what you were aiming for, just happening to hit something ehind it would be really, really unlikely. Then again you can already hit something in darkness that you can't even see so...
RavenRed: More in the sense of your arrow shooting off into the middle distance than anything else. It also means that if you shoot an arrow into a packed mass of orcs, you're moderately likely to hit SOMETHING, if not by the first, then certainly by the tenth in line...
LogrusMage: Actually, it wouldn't be that unlikely, especially with a big croud to fire into. In realworld battles featuring archers, this was a common occurance. As the enemy approached, you'd first enter the barrage stage. As soon as the enemy entered barrage range (the maximum distance to which your bow can lob an arrow if not worried about aiming), you start lobbing, and some will find marks. Then, as what's left of the opposing army gets closer, and enters a range at which aiming is actually feasible, you switch tactics and start firing shots aimed at targets, instead of just aimed in a general direction as with the barrage stage. Even then, usefully hitting a target other than the one you're aiming at when firing into a large infantry formation is quite common.
NeilStevens: Keep in mind misses can also hit walls, ceilings, floor... I could see this happening a percentage of the time, but not for every miss. Oh, and some misses represent hitting the armor and doing no damage.
RavenRed: All true, and especially true for bowmen who "Arch" their shots moreso than Crossbowmen (who will be absent from 3.0.0 anyway)... however, it might be a nice POSSIBLE effect for a miss...
TheFalcon: Maybe in open dungeons, it would be possible to hit something in the middle of a group of monsters, by firing over the others, but not in roofed dungeons. This might add some more realism. (It would also change something that annoys me with archery at the moment 
).