So, what haven't I played? NRBH, but Battlefield Integrity stands out.
I have never tried an Infantry overrun.
I don't think I have ever played with either raised or sunken roads. I have climbed cliffs, but not scaled buildings. There's probably quite a few terrain types I have never played in. I don't think I have played with hedgerows as they are currently written.
I hav never used Steppe Terrain, though 'Clash along the Psel' has been on my bucket list forever. I have never used cannister. I have never played with recorded possession of Panzerfausts.
I have never used neither general nor specific collateral attack. I have never done any airborne assaults, though I played the SL version of 'Rehearsal for Crete'. I have never played with ski rules, though I used skis plenty before, during, and after my military service. I have never use boats or swam. I have never used Vehicular Smoke Grenades. I have never used Animal-pack, nor tried to Animal-pack a non-Pack Gun

I have never used a Dare-Death Squad(I may have had one used against me). I have never used NOBA. I have never played a CG to the bitter end, as most have ended with one side resigning.