The most widely used Mac client, IRCle has all the features that many like. Because it's so widely used, development and support still continue for this popular client. See the homepage for many documents on it's use and functions.
: IRCle website :
MacIRC, while still in beta versions, is probably the second most popular Mac client. If IRCle isn't what you'd like, give MacIRC a look.
: MacIRC website :