Hey, because it is always handy to have a quick command reference, here are a few useful ones that I sometimes need to find quickly. I will try to keep it up-to-date.

Interfaces

Display the interface part of the configuration show configuration interfaces

Quickly check L1 and L2 status (BPDUs, tx and rx errors) show interfaces <interface-name> media

SFP/Transceiver/Fibre checking show interfaces diagnostics optics <interface-name>

List all interfaces with their IP show interfaces terse

Find out which interface is part of which VRF show interfaces routing-instance all terse

LACP

Show the status of all LACP interfaces: show lacp interfaces show lacp statistics interfaces

ARP and NDP

Display the ARP table (ipv4) show arp

Display the ND table (ipv6) show ipv6 neighbors

Hardware troubleshooting

Temperature and fans show chassis environment

Serial numbers and PID show chassis hardware

System troubleshooting

Display the system part of the configuration show configuration system

Uptime and NTP show system uptime

NTP servers show ntp associations

Check the proper DNS resolution of a FQDN show host example.com

Currently logged-in users show system users

Last configuration changes with time and date show system commit

System and modules version show version

Routing protocols troubleshooting

IS-IS

Show the IS-IS part of the configuration show configuration protocols isis

Show on which interfaces is IS-IS running show isis interface

Show on which interface IS-IS actually established an adjacency show isis adjacency

Show IS-IS route database show isis route

Show IS-IS link state database show isis database

Show IS-IS routes that are actually installed in the RIB show route protocol isis

BGP

Display the BGP part of the configuration show configuration protocols bgp

Display a summarized version of the BGP neighbors (I highly prefer the Cisco one) show bgp summary

Display detailed information about a particular BGP neighbor show bgp neighbor <neighbor-ip>