Gettin' Jiggy with Magic Missile
So okay, here's an idea that I just had: Say your wizard advances to 6th level, and as his new 3rd level spell he selects Magic Missile again, having already learned the first level version. What this would do, according to my nefarious idea is increase the base damage of the spell to 1d6+2 per every odd-numbered level (so 3d6+6 for our hypothetical 6th level wizard, plus any applicable feats, of course, ahem). And the same would apply if the spell was learned again in place of a 5th level spell, except that in that case damage would be 1d8+3 per missile. [So we're talking 4d8+12 total damage from a first level spell that the 7th level wizard has burned a third- and a fifth-level slot upon in addition to the 1st-level slot to begin with. Regardless of those higher level slots, it would be prepared and used in a first level slot. However, for purposes of magic resistance and invulnerability effects it would be treated as a third- or a fifth-level spell. Is that too weird? Too unbalanced? Maybe barely plausible/playable?]