A 60-ton BattleMech. It's a clanner OmniMech. Inner sphere designation Vulture.
Mad Dog has a very distinct shape - The cockpit part is roughly triangular with sides (same size as the middle cockpit part, slightly smaller) having places for missile launchers. It has short "hands", and Timber Wolf-like legs (like Timber Wolf, it's a chicken-walker).
Mad Dog is, due to its structure, used typically as a missile 'Mech - the alternate configuration that has only gauss rifles doesn't even look like Mad Dog anymore! Usual configurations use LRM-20s, SRM-6s and Streak SRM-6s, with lasers, autocannons and PPCs as auxiliary weapons.
The 'Mech is used by all clans, but none of the clans uses it more than Clan Ghost Bear and Clan Smoke Jaguar.
Information from Technical Readout 3050