The Big Fucking Gun (or more politely, Big Freaking/Fragging Gun) found officially in all of the high-profile id Software games like Doom and Quake. Fires a very large green ball of man-made lightning and then upon impact, the weapon instantly releases a huge spread of energy to anyone that the BFG'er is facing. (Despite how extensive this definition is, it is loose.) In Quake II, the ball of energy will shoot lasers a certain distance for some additional pain.
Newbies hate the weapon, but some veterans consider the BFG a thinking man's weapon (in deathmatch)because of its strange behavior, slow firing rate, and high energy drain.
Grasshopper couldn't hide from ShadowFox's BFG.
Neo was disintegrated by Bar3Star's BFG.
A game mode featured in nearly every shooter (simulator or FPS) that allows you to blow the living crap out of your opponents. It was popularized by Doom and pretty much made it a requirement for every shooter in the market after. These days multiple modes of deathmatches (like Capture the Flag and Team games) exist.
Find a buddy, start a game, and beat the living snot out of him. Do it again in another way. Repeat until you have the most kills. That's the basics of DeathMatch.
The Mad Cat was the first Clan 'Mech to be seen in the Inner Sphere, and is likely the trademark 'Mech of all of the Clans because of its incredible versatility, speed, and staying power. Massing at 75 tons and moving as fast as most Inner Sphere medium 'Mechs, the Mad Cat supposedly gets its name from the boxy missile pods of a Catapult (Cat) and the dual-laser arms of a Marauder (the designation of the Marauder was MAD, i.e. MAD-5T).
Unless you're in a Clan 'Mech of your own or in something larger, steer clear as just one in any configuration will ruin your day.
The mercenary MechWarrior shifted to his right a little to look out the side of his viewport. He thought he saw a Catapult at first, but upon closer inspection it had arms going out from the missile pods. "What is it?" he cried on the radio. "That's the craziest looking Catapult I've ever seen!"