Shei-kun:
430. I am not allowed to use my knowledge of physics to create a hydrogen bomb with the Create Water and the Major Creation spells.
In one of the older AD&D editions, it specified that an item conjured by Major Creation (or the spell it was based on) would shrink until it disappears at the end of the spell. So, one makes a hollow metal sphere and fills it with water. This sphere then shrinks without letting any water escape, thus compressing it until it reaches critical mass. Best part is, you can create it and just leave it there, thus giving ample time to escape the blast radius.
They never saw it coming.
Why do this when 6 walls of force constructed in a cube pattern, a Decanter of endless air, a Bottle of endless water, an Efreet bottle, a rabid gnome who is obsessed with magical items, and a wand of Mordenkainen's Disjunction work just as well?
OK, so the other is more practical....but this one is more fun...
433) I shall not ever consider doing the above in an actual game, whether I am a mad wizard PC or the GM.
434) I shall stop asking the GM "Hi, what's your name" whenever he introduces a completely insignificant NPC (shopkeeper, innkeeper, stable boy, page, etc)