Changing Cisco Equipment Hostnames

[Charger1129]

Hello. I recently started working in a network that the hostnames on all the devices (switches, routers, firewalls, etc.) are an absolute mess and I'd like to put some standard naming conventions in place. 

Is there any impact on any devices such as a switch, stack switches, router, firewall, wireless controller, etc. that would occur because of such a change? 

[Leo Laohoo]

No but if your DNS is tied to the old hostname, you'll need to fix that up too.  

[LJ Gabrillo]

Yeap as Leo Laohoo said,

To add on that, if you are using P2P serial connections that uses the hostnames of the routers, well you need to coordinate with that, but there is a workaround on that though, so no worries. :)

[o.melendres]

Should generate SSH key as well, which is tied to the hostname and domain name,

# show crypto key mypubkey rsa