The arrow spells from CoR are kinda shitty as actual spells, but they make amazing traps. Put arrowsplit into an auto-reseting trap on your bow with the trigger "when an arrow is fired from this bow'. For hilarity, make it a splitting bow. Now, whenever you make an attack, you get 10 (2 from splitting x 5 from arrowsplit). Do it with hand crossbows instead and TWF + rapid shot with them. Assuming +16 BAB, rapid shot, and full TWFing with two splitting hand crossbows of speed, you're looking at 10 attacks, each of which becomes 10, for a total of 100 attacks per round. Throw on a doublestrike trap and you can hit two targets with each attack.