Partially due to some fun sounding rules/equipment in the crimson slaughter book I'm tempted to give chaos marines a second swing. (the first time kinda fell short due to lack of direction on my part), and I kinda have a general idea for an army idea for a fast khorny assault based army.
It’d mostly centre around a khorne lord on a juggernaut backed up by a group of bikers to race for something important but killable (e.g tau pathfinders) and them move from target to target to disrupt. then maybe a maulerfiend or two as some more fast assaulty bricks. add to that a pair of hellbrutes being babysat by a warpsmith for some 2nd wave assaulting (as they move much slower) and minor shooting. add a couple units of marines for some objective grabbing and deployment zone support.
I know it’s far FAR from a strong competitive list, but that’s not really my sorta play style to begin with but it seems like something that could be fun to use and follows a strong theme, though I'm always open to suggestions