AdiIRC

Added in 1.5

/ignore [-cdiklnprtuNwx] <on | off | nick | address> [type] [network]

Ignore certain types of messages or all messages from a user.
/ignore with no parameters will show current ignore status.

The nick will not be hidden in the Nicklist, and join/part/quit/mode messages will not be ignored.
If you have a query window open with the nick, the query messages will not be ignored until you close the query window.

Switches

-c - Ignore channel messages.
-d - Ignore DCC requests.
-i - Ignore channel invites.
-k - Ignore control codes.
-l - List all ignores on current network.
-n - Ignores notice messages.
-p - Ignore private/query messages.
-r - Remove ignore.
-t - Ignore CTCP requests.
-uN - Remove the ignore after N seconds.
-w - Apply the ignore to any network.
-x - Indicates address should be excluded.

Parameters

<on | off | nick | address> - Turns on/off the ignore feature, or if a nick/address is specified, applies the ignore to that user.
[type] - Ignore by hostmask, see $mask for available types.
[network] - If specified, applies the ignore on that network, otherwise applies the ignore on the current network.