If you are testing network connectivity, packet loss, latency, etc. and you need an external server to ping (ICMP echo request), consider using the IP 188.8.131.52. This IP represents Google's public DNS.
Funny, in the past, I remember using 184.108.40.206 and never knowing exactly who it was that ran that IP. Turns out, as with most things strange and interesting on the net, there is a small story behind that IP. Kudos to Tummy.com for posting it!