Cool that you've built a tattoo needle. You can practice on grapefruit skin. Or one show I saw they used pig skin from a store (not fun IMO).
Just don't jump into it, (some friends got BAD one's in H.S.).
I had a GF with bad one's and I wanted to hunt whoever did them too!
You could try something related and do levitation with fishhooks.
(Saw it on a show)

I don't think I'd EVER get that bored though.
Just don't ever get into those huge plug earrings (I just don't understand those)!!!
Maybe try building Homemade night vision or a bionic hearing device.
You could integrate that onto a cannon somehow.
I have a book showing how to convert fisher price camera into IR vision.
(But it's kind of old so... IDK). 8)
EDIT:
this Book I noticed you said not to complicated electronics but it's a simple book with cool projects and you could probably learn from it (It has lightning globes etc.) 8)