Unless you can find blockchain based cryptocurrency which allow zero tx fee and their block isn't full (which means 0-conf is safe), i suggest you to use DAG based cryptocurrency such as IOTA, byteball and RaiBlocks.
oh dear, that did it after i told him his left ball would not fall off and your talking about "byteball"
RaiBlocks I think is the one that uses gossip about gossip and works like a data stream and is another
name that pops up a lot but I didn't really understand it to see how it store data so many I am getting
too old for new concepts like that.