There are huge number of ports which are reserved. But the ports mentioned below are more important.

IMPORT PORTS:

20-FTP Data

21-FTP Control

23-Telnet

25-SMTP

53 -TCP

69 -TFTP

80 -HTTP/WWW

109-POP2

110-POP3

123/UDP-NTP

137-NetBIOS

443-HTTPS

546-DHCPv6 client

547-DHCPv6 server

Friends if you feel still there are some ports which are more important. You are welcome to update it.

Thanks