Crimpers, cables, adapters, and console access for when the network fights back.
Pass-Through RJ45 Crimper Kit
Pass-through connectors ended my crooked-crimp era. Push the wires all the way through, verify the order, crimp and trim in one squeeze. Get the kit with connectors and boots included.
Carry short ones. Everyone has a 25-footer; nobody has the 1-foot cable that keeps a rack tidy. An assortment of 1/3/5-foot cables makes you the hero of every cabinet cleanup.
The cable that separates engineers from tourists. When the switch is bricked and the web UI is gone, serial console access is the only door in. Keep one in every bag you own.
Modern laptops forgot Ethernet exists; your job didn't. A 2.5GbE adapter is the same price as gigabit now and makes packet captures and big transfers painless.