1) Shadowflame knife, better dps than a megashark, bounces, does DOT, takes no ammo or mana and uses the melee damage type. Its my primary weapon from the start of hardmode all the way to golem.
2) Shadowflame hex doll, just such a fun and creepy attack to use and with an endgame mage build you can fire almost continuousl.
3) Once got a large solar erruption because apparently weapons can get impossible prefixs on spawn (though I've only seen it in flails) was interesting being able to hit things off the screen with melee.