Spanning Tree: L2 protocol to transform complete network failure due to topology loop into a never-ending series of more subtle failures.
Per-Vlan Spanning Tree: L2 protocol designed to transform complete network failure due to topology loop into up to 4094 smaller failures.
VRRP: a mechanism by which the possibility of an outage due to loss of a router is replaced by the certainty of an outage due to VRRP.
ARP: a protocol to launch periodic, unannounced stress tests of network infrastructure.
IP Multicast: awesome solution in search of a suitable problem, for at least 25 years.
RIP: a routing protocol which no-one will admit to using.
IGRP: a routing protocol which no-one should be using.
IS-IS: a routing protocol which no-one thinks of using.
DVMRP: a routing protocol which no-one has even heard of using.
ASN.1: Leftover cruft from when TCP/IP was deployed "as a stepping-stone to eventual deployment of the OSI suite of protocols."