How about a combination APFSDS-3P round that can go through 3 blocks of apartment buildings and then explode?  Kinda like combining the best of direct and indirect fire.

 

Or a 120/125mm version of the 12 gauge 'Dragon's Breath' round?  That could cause anyone to soil their fatigues.  Probably not all that useful, but touch one off at night and enjoy the show!

 

Finally how about a low-velocity/short range demo charge?  Low velocity allows for a larger/heavier warhead without exceeding normal pressure levels in the barrel. 

 

Bring back something of the old British AVRE..., if not launching the "Flying Dustbin" then delivering a capability a whole bunch like.