Ossiarch Bonereapers (OBR) sounds like just what you want.
They are very elite, have many and varied centerpiece models (Katakros is gorgeous), and are probably the best meat grinder in the game (tanky and still fairly killy).
Their main weaknesses are speed (which can be mitigated with RDP usage, battleline banners, and the run and charge faction) and being shot to death (still figuring out what I can do against this lol).