Who are the best teachers for ipcc ?

All teachers are average. I know about every teacher mentioned above very well.

For Law - Mayank Jain (he will help you to learn the concept with complete understanding)
For Ethics & Communication - PS Rathore (Best for theory subjects)
For Costing and FM - Ashish Kalra or RK Mehta 
For Taxation - Ajay Jain or MK Gupta

For CAFM - Mohit Jain is very bad for FM. I took two demo classes from him. I took classes for CAFM from Ashish Kalra, he is far better than other teachers. Just due to him I scored 74 in CAFM. I don't about teaching style of RK Mehta but he is also very popular among students.

For Tax - I did self study but friends I came to know that Ajay Jain and MK Gupta are better than other teachers. 

For Law - Please follow my advise, no one else can be better than this combination. Mayank Jain for Law and Ethics and Communication by PS Rahore. My cousin and two of my friends followed this advise and they thanked me for that later. I can bet no one can be better for this subject other than them. In law you need to cram many things for exam. Mayank Jain and PS Rahore are only faculties in the market who help you to cram those things.

Thankyou Rohit for your valuable advice .