Four Color To Fantasy, with its gp deficit rules that allow to trade a gp deficit with power.
Tournament Fair and Taverns with the Degree of Success rule, that allow you to have chase scene with the monster behind the characters in a funny yet simple manner game-wise.
101 Arcane Spell Component from Philip J Reed, a knowledge arcana check DC is given to a number of component, beating this DC allow you to know how to use this component in the casting of a spell. Actually using it require one or more round added to the spellcasting, a spellcraft check (each component has its DC), and having the component (which has a gp cost).