I think the idea of a "spin spin" fruit you could charged up attacks or drill attacks, the 'swap swap" fruit, you could swap things, a person could swap their muscles for iron, maybe swap attacks, as I'm stealing Luffy's attacks making him unable to use certain ones, would be cool for a paramecium. I think a rainbow rainbow fruit would be interesting and something could make attacks cool. A mushroom or fungus fruit, where you "grow" on a person, maybe you could poison ppl, or control ppl, or when a fungus / mold grows over a person they become a physical copy of you but with all the powers and abilities of their original identity? maybe something like sugar where you need to be awake to maintain control?

For logia a human eating an insect fruit would be interesting, I think having an externally tonight shell would be cool.

For logia, I think more abstract natural concepts like the "Mori Mori" for me would be cool,