For servers it depends. If you are going all-out, InspIRCd is what I roll. The only complaints I have with it are the massive config file (~2800 lines with the main config and the module config, more if you count the lesser files). The server for getting and going is UnrealIRCd, which is what I used to run. Solid and basic, just with a few less features.

For clients, I use Hexchat, which ill fight for as the best graphical client. The only thing mIRC has going for it is its legacy of scripts and people that still use it. For command line clients, ircii and weechat are good, especially coupled with tmux. I don't use them, but the people that do love them.

Also, if you want a bouncer, ZNC is great. Would highly recommend if you have a free server with a stable connection.

I like Textual on macOS. It's rather nice.

EDIT: Since this seems to be unclear: I was referring to the second question regarding IRC clients.

I still just use Pidgin. It ain't fancy (neither is IRC), but it also works a client for hangouts and some other things and has a portable apps version.

For Windows I always use Hexchat, which seems to be the only decent open source client for Windows. If anyone would like to jump in and point out others I don't know about, by all means.

(Heck, it's what I use on Linux too)

I would recommend ircd-ratbox, which is the fork of ircd-hybrid most used on efnet.

I run an IRC server with UnrealIRCd. Works well.

ircd-hybrid on debian, personally.