Of all the call blocker I have used, Mr. Number Callblock is the best. NQ Mobile's Call Blocker and Call Control are just no match. Of all 3, Mr. Number's free cost is genuine, while the others try to make you pay or you will be annoyed with certain things like limited blocking, constant promotion reminder, etc.
Call Control also had one problem, I think. That it somehow buzzes my phone from time to time for no reason. I think it is due to the loading and unloading of the app arbitrarily because it vibrates every time it is turned on. It's acting like the ringtone function.
Of the 3, Mr. Number also cuts down blocked call's ringer/vibration most.
Simply, the best thus far.