I'm also a fan of the Arctic Fox. If by chance you are hauling some of the few humanoid battle armors the Lyrans have, GD and IS standard and GD scout, the Arctic Fox is a decent taxi. Besides that the Fox has alot of firepower for it's size on some of it's varients.
Then there are the ever dependable guys like Enfields, Starslayers and Lynx.
As for assaults, I think the Hauptman is my current favorite, because of the new varients. The Hauptman is already fun because it's one of the few high tonnage assaults Lyrans make that isn't about fitting as many of some weapon on the chasis as possible. The OD varient provides one of the few C3 Masters the Lyrans make on a sturdy and reliable, well armed frame.
Other assaults i'm fond of are the Fafnir (draws a ton of fire, or just plain murders things) the Beserker, Banshee 6S and 7S, most models of the Zeus and the Battlemaster 4S.