I've done a Richter Run with no saves through both Castles. I've almost made it to the last save room, but always died over those corridors in Olrox's Quarters (Inverted) where you get endless spikes. I've always wanted to go back to completing this run.
I think the world record is 6 minutes, I made it to where I did in around 15-20 before dying.
Also the Luck mode changes your stats and increases the game's difficulty by a bit.
As for other CV games:
- Harmony of Dissonance with no accessories equipped, no whip tips, no upgrades (avoided all HP & MP Plus), nothing but the Vampire Killer and Subweapons through the whole game.
- POR Level 1 hard (new file)
- POR Sisters Level 1 hard
- POR Richter/ Maria Level 1 hard (up to Dracula)
- OOE Shanoa Level 1 hard (new file)
- OOE Albus Level 1 hard (Up to Dracula)
- Vampire's Kiss, true ending (Yeah, it's hard enough to be listed here)