Dear Hemanth Sai,
You cannot really say that a particular topic is important in IIT-JEE but here i am giving you some topics from Physics,Chemistry & Mathematics that are a little more scoring than the rest of the topics !!!
1.Modern Physics(X-Rays,Photoelectric Effect,Atomic Physics)
3.Mechanics(Rotational Motion-More important)
4.Work,Power & Energy
5.Reflection & Refraction of Light(Optics-V.important)
2.Properties of elements in the Periodic Table
4.Rates of Chemical Reactions(Chemiical Kinetics)
6.D & F block elements(Remember the reactions)
8.Organic Chemistry(Full-Highly Scoring)
9.Solutions & Thermodynamics(Scoring)
1.Complex Numbers(Easy & Scoring)
2.3D Geometry(V.Easy & Highly Scoring)
5.Circle,Parabola,Straight lines(Simple & Scoring)
6.Definite Integration(V.Easy & Scoring)
Best of luck
Hope this has helped you !!!!!
Hope that you are definitely going to approve my answer by clicking 'Yes' given below........ Plz.........