There's quite a lot of these on Hawkee, but I just wanted to post my own one. I think it looks better, too (not being big headed, lol). Paste in remotes (ALT+R) and type /ASCII.

The Character Number search will highlight the Nth character in the list. The Symbol Number will get the number you put in the edit box and return the symbol in the box below. This shouldn't be hard to use.. there's a help box at the far bottom that tells you what you're hovering over.

You may notice that this comes directly from my MP3 Player, but eh, this is for people who haven't got it.

dialog ASCII {
  title "ASCII"
  size -1 -1 260 140
  option pixels 
  list 1, 1 1 115 95, vsbar size
  button "Copy to Clipboard", 2, 2 97 115 20, flat
  button "Close", 3, 2 117 115 20, flat
  edit "", 4, 130 15 55 20
  button "Search", 5, 190 15 55 20
  box "Character Number", 7, 120 0 135 40
  edit "", 8, 130 55 55 20
  button "Search", 9, 190 55 55 20
  edit "", 10, 130 78 100 20, read
  box "Symbol Number", 11, 120 40 135 63
  edit "", 12, 120 105 135 33, read autovs multi
}

alias ASCII { dialog $iif($dialog(ascii),-v,-md) ascii ascii }

on *:dialog:ascii:mouse:*: {
  if ($did == 1) {
    did -ra $dname 12 This is a list of $crlf $+ ASCII characters.
  }
  if ($did == 2) {
    did -ra $dname 12 Use this to copy what $crlf $+ you have selected.
  }
  if ($did == 3) {
    did -ra $dname 12 Use this to close the $crlf $+ dialog.
  }
  if ($did == 4) {
    did -ra $dname 12 Type in an ASCII $crlf $+ number here.
  }
  if ($did == 5) {
    did -ra $dname 12 Click this to search $crfl $+ for an ASCII character.
  }
  if ($did == 8) {
    did -ra $dname 12 Insert an ASCII symbol $ctrl $+ here.
  }
  if ($did == 9) {
    did -ra $dname 12 Use this to search $crfl $+ for an ASCII symbol.
  }
  if ($did == 10) {
    if (!$did(10).text) {
      did -ra $dname 12 Search for an ASCII symbol.
    }
    else {
      did -ra $dname 12 This is the ASCII symbol $crlf $+ you searched for.
    }
  }
}

alias -l chars {
  did -a $dname 1 -----------------
  did -a $dname 1 NOT ALL ASCII 
  did -a $dname 1 CHARACTERS
  did -a $dname 1 WORK IN mIRC,
  did -a $dname 1 SO EXPERIMENT!
  did -a $dname 1 -----------------
  var %x = 1, %y = 255
  while (%x <= %y) {
    did -a $dname 1 $chr(%x)
    inc %x
  }
}

on *:dialog:ascii:init:0: {
  did -b $dname 5,9
  $chars
}

on *:dialog:ascii:edit:*: {
  if ($did == 4) {
    if (!$did(4).text) {
      did -b $dname 5
    }
    else {
      did -e $dname 5
    }
  }
  if ($did == 8) {
    if (!$did(8).text) {
      did -b $dname 9
      did -r $dname 10
    }
    else {
      did -e $dname 9
    }
  }
}

on *:dialog:ascii:sclick:*: { 
  if ($did == 1) {
    if (!$did(1).sel) {
      did -b $dname 2
    }
    elseif ($did(1).sel) {
      did -e $dname 2
    }
  }
  if ($did == 3) {
    dialog -x $dname 
  }
  if ($did == 2) {
    clipboard $did(1).seltext 
    dialog -t ascii ASCII: Copied to clipboard
    .timercop 1 1 dialog -t ascii ASCII
  }
  if ($did == 5) {
    if ($did(4).text > 255) {
      noop
      $input(Please do not enter a number above 255.,uwo,Error!)
    }
    else {
      did -c $dname 1 $calc($did(4).text + 6)
    }
  }
  if ($did == 9) {
    did -ra $dname 10 $asc( $+ $did(8).text $+ )
  }
}