High-weightage topics hold very much importance in examination like Joint Entrance Examination Advanced, as here is depends on how accurately you answer the questions as even if your number of attempts is less, it more depends on them being right. Some of the important topics are:

Physics:
Electricity
Optics
Modern Physics
Magnetism
Laws of Motion
WPE
Thermodynamics
Waves and Oscillations

Chemistry:
P Block
GOC
Alcohol Phenol and Ether
Electrochemistry
Bonding

Do these chapters and you'll definitely emerge victorious! Hope I have answered your question. All the best!