So for me (also do IT/Security consulting and repair) I have:
- Clonezilla (multiple versions for different CPU architecture as well as x86 and x64 boards
- DBAN (only for HDDs)
- Hirens Boot CD (for Window OS repair/password resets)
- GParted (same setup as Clonezilla)
- Kali Linux (for security auditing and malware analyzation)
- Puppy Linux (for general stuff/data rescue on old computers/anything I need to boot into RAM for)
- TAILS (it is intended for heavy privacy and security but I actually don't really use it, but it's small so I leave it on there)
- SystemRescue (Linux distro for all sorts of rescue purposes)
- Sometimes a Windows install/recovery ISO (per need basis, typically Hirens solves recovery stuff so I rarely go this route for recovery)
EDIT: Also have two versions (x86 and x64) of AntiX for general purpose stuff. Boots into RAM like puppy but I find it a little more useful.
I have these running on a 128 (I think, might be bigger) flash drive that I actually have looped on my keychain. I have found that 90% of the things I need to do can be done from that, and having it on my keys means I always have it ready. Unless I lose my keys for a while that is...