Listed below are a few IRC Chat Clients.
I recommend mIRC if you use Windows.
In all cases, if it says "FREE" double-check as to whether it is freeware or simply a free trial.

mIRC for Windows (30 day free trial) then $20.00 USD to receive new updates for three years.

Colloquy for Mac OSX & iPhone & iPad (Free, but will accept donations)

Igloo IRC for iPhone & iPad ($6.99 USD)

adiirc for Windows (Free, no strings)

Textual for MacOS & iPhone (30 day trial then $5.99 USD

irssi for Linux, Windows and Mac (Free)

XChat for Windows, Linux and Mac Systems (Free)

Palaver is an advanced IRC client for iPhone and iPad featuring a unique user interface which makes using IRC a pleasure. (I do not know the price.)

Hexchat for Windows and Linux (Free)

Here you can download the official release packages of KVIrc. The official packages are released least frequently but are also the most stable ones. (Free and Open Source)

AndroIRC for Android Devices (Free)

IceChat for Windows (Free)

WeeChat for Windows, MAC and linux (Free)

MsChat 2.5 for Windows (Free)

HoloIRC for Android (Free and Open Source)

BransonIRC 2.0 Client by Branson (Free)

BransonIRC 2.0 Source Code by Branson (Free)

Quassel IRC [Quassel 0.14.0] For Windows, linux and MAC OS

IRCCLOUD native apps for iOS and Android. Priced from Free to "Contact Us"

Mermaid's MSChat2.5 site for Windows Free to use.

Good mIRC stats program [We use it on] Free to use

Icons8 Free for non-commercial use (Used for the favicon on this site)

Cool Text Graphics Generator Free (Used for the page logos on this site)

I haven't actually used the next two as I haven't learned how to do so as yet.

Free PHP Scripts

XML Sitemap Generator