5-foot rule: Whenever an adjacent foe attempts to take a 5-foot step away from you, you may also make a 5-foot step as an immediate action so long as you end up adjacent to the foe that triggered this ability. If you take this step, you cannot take a 5-foot step during your next turn. If you take an action to move during your next turn, subtract 5 feet from your total movement.

Critical success & failure: If you roll 20 on a skill or an attribute check, you may roll again and add roll-10 (min 0), if you roll another 20, you may roll again. If you roll 1, you must roll again and reduce your result by roll-10 (min 0), if you roll another 1 you must roll again.

http://www.d20pfsrd.com/gamemastering/tools/critical-generator

Spellcrafting Divine spells if you are an arcane caster gives a -5 penalty and vice versa