Change your OSX MAC address to a random value. If you don't know why this is useful, you probably don't need it.

new_mac.py

#!/bin/bash
# OSX MAC address changer
# glenn@sensepost // @glennzw

# This script will disaccociate from the current AP, randomly change your WiFi MAC, and then reassociate.
# N.B This code is specifically for OSX

iface=en1

ap=$(airport -I | grep SSID: | grep -v BSSID| sed 's/.*SSID://' | sed -e 's/^ *//g' -e 's/ *$//g')
echo "[+] Disassociating interface '$iface' from SSID '$ap'"
airport -z
sleep 4

old_mac=$(ifconfig en1 | grep ether| sed 's/ether //')
new_mac=$old_mac

echo "[+] Original MAC: $old_mac"

while [ "$old_mac" == "$new_mac" ]; do
	tmp=$(openssl rand -hex 6 | sed 's/\(..\)/\1:/g; s/.$//')
	echo "[+] Trying to set MAC: $tmp"
	ifconfig $iface ether $tmp
	sleep 3
	new_mac=$(ifconfig $iface | grep ether| sed 's/ether //')
done
echo "[+] Successfully changed MAC address!"

echo "[+] Re-associating to '$ap'..."
networksetup -setairportnetwork $iface "$ap"
echo "[+] Done!"