ASF - AeroSpace Fighter
Black Wolf - the original Clan name for Mk. II. Originally mentioned in MW4 manual - the game for which it was created - but has since then been ignored everywhere, starting with TRO3067.
Demo - Demolisher tank
Easy mode - Timber Wolf/Mad Cat B, named because of its powerful long-range direct-fire weaponry (Clan Gauss, two CERLBL's, five CERMBL's, two MG's)
Flying Beatstick - Shiva E, armed similarly to Mk. II A: with two LB-X 20 and two LB-X 10 AutoCannons
Glass cannon - any unit that has light armour relative to its firepower, eg. Osiris C with twin PPC's
Holly - Hollander II
JJ - JumpJets
Jumpin' Jack Flash - Novacat with jumpjets
Mr. Bubbles - Atlas A, named after the three Rotary AutoCannon 5's
Partyvan - Partisan
Scalpel - Morrigu B, named so because of its armament - 3 Clan Heavy Large Lasers.
Scat - Shadowcat
Steiner Scout - in Lyran Commonwealth, Atlas scout you! (More specifically, the Atlas E aka "Master and Commander")
Siege Engine - Black Wolf/Mad Cat Mk. 2 E, armed with 4 Clan Ultra AutoCannon 5's and two ATM-9 launchers. Able to deliver immense amounts of firepower to medium range. Also a glass cannon.
Thanny - Thanatos
Timby - Timber Wolf, IS reporting name Mad Cat
Whammy - Warhammer
EDIT: moar is moar