Blades to cut, rope and anything to bind yourself really tight, ice or candles to burn yourself, spikes to stab, your own teeth and nails if you're motivated enough, bottles and likes for penetration if you're into that, acids, with imagination everything can be used to hurt. But I'd still advise against it.
Alcohol, salt, lemon juice are incredibly painful on bare flesh if pain is what you are searching. If you want to just see yourself butchered, blades with teeth would be nice visually I think.