Optical Power Meter, also an RJ-45 coupler and a long patch cord, that way you can go and sit in comfort somewhere while consoled up to switch. Others have mentioned this too but also a good VFL (visual fault locator) if you work with fiber. Make your company pay for these things unless you’re like me and want to take tools with you to the next job, and you do work on the side.
Edit: Adding Snips! Learn how to hold and use them.
Klein Tools 21010-6-SEN Free Fall Snip, Carbon Steel https://www.amazon.com/dp/B00HAN2RRY/ref=cm_sw_r_cp_api_glt_fabc_SY2N7FM7W3FV5VXD32V3?_encoding=UTF8&psc=1
Fluke Networks MT-8200-60-KIT IntelliTone Pro 200 Toner and Probe Kit, IntelliTone Probe and Toner Kit https://www.amazon.com/dp/B00N2S6RPY/ref=cm_sw_r_cp_api_glt_fabc_BD400BK8ZZEQ8NQXGCST
Also Klein makes great tools I carry the following screw drivers: 11-1, a flat head, and a micro 4-1 (all non ratcheting)
Klein Tools 32500 Multi-Bit Screwdriver / Nut Driver 11-in-1 Multi Tool, 8 Industrial Strength Bits, 3 Nut Driver Sizes, Cushion Grip Handle https://www.amazon.com/dp/B0015SBILG/ref=cm_sw_r_cp_api_glt_fabc_C8JX8H7RSA1RAPZ2X0H7
Precision Screwdriver Set, 4-in-1 Electronics Screwdriver with Industrial Strength Phillips and Slotted Bits https://www.amazon.com/dp/B01EOY7LTA/ref=cm_sw_r_cp_api_glt_fabc_TXPYFR74Q7CKJDJTJJGJ
Fluke Networks MT-8200-60-KIT IntelliTone Pro 200 Toner and Probe Kit, IntelliTone Probe and Toner Kit https://www.amazon.com/dp/B00N2S6RPY/ref=cm_sw_r_cp_api_glt_fabc_BD400BK8ZZEQ8NQXGCST
I have had a few toner probe/generator combo kits in my time.
I will throw my lot in with the Klein scout pro, just make sure to get the PoE version and cover all your bases. When I got mine I didn't know there was a PoE one and have been kicking myself since. Great little tester that I have had no problems with.
However the toner wand that comes with many of the kits, the Klein pro probe tracing tool I've never been able to trust. the buttons are too pronounced and more than once I've found it on in my bag when it shouldn't be or dead. The batteries corroded within maybe 3 months of being in my bag and I have had to clean the entire compartment out with baking soda twice. The end of the tone probe doesn't screw in with threads it's a twist lock, which it seems to twists itself loose.
Greenlee used to make a toner/tonerwand kit for their Greenlee 500xp series that is what is on my toolbelt. Both are 9v and work every time I use them, never had an issue. Sadly it looks like they have been discontinued, because the kit used to be a little cheaper than the fluke kit.
Fluke Pro3000 Toner and wand : If you need a toner and toner probe this is probably the best bang for your buck you are going to get. Great deal on a combo set. When I worked as technician we either got issued these or the greenlee's and they both stood up very well, If I had to buy one set today it would be this one.
Call me old fashioned but I prefer a set of Electrician Snips. They will cut anything you need them to (and many things you shouldn't) as well as have strippers on one of the blades for 19 and 23 gauge wire.