It's will depend on the your skills experience and knowledge.. But max package range of 6 to 10...and important subjects in mechanical are TOM, design, Som, thermodynamics and manufacturing...
Package in mechnical engineering is completely dependent on your performance and experience in that area. You may get package more than 1cr also.
Telling about best subject - IC engine, Thermodynamics, Mechatronics and Machine design are some of all time importamt subjects. All of these needs better understandings and have wide scope in every individual area. Even there is wide scope for research and development in this subjects.
The package for mechanical engineer is around 6 to 7 lac. The main subject of mechanical are thermodynamics, design, theory of machine, manufacturing processes, etc. The best subject i like is design