This exploit will allow you to get a double crit, and is great for healing a drained target back to full quicky.
Step 1-Cast Divine Favor
Step 2-Start Casting Holy Light (Or FoL, if you prefer)
Spet 3-Spam Holy Shock while the HL or FoL is casting.
If you followed these steps correctly, both your HL/Fl AND your Holy Shock will get the 100% Critical Chance from Divine Favor.
Additional note: This requires low latency (Less than 100) and at least 25 FPS.