Among high quality knots, the butterfly loop is perhaps the easiest to remember how to tie correctly. Start by simply making two twists in the same direction to form the two loops. Then wrap the outer loop around the standing part and pull it through the hole of the inner loop.
The Non Slip Loop Knot. Superb. The strongest loop knot you can tie. Used by big game anglers worldwide. Easy to tie, far stronger and more reliable than the old fashioned strangulating figure eight knot that can substantially weaken line. Ultimate Knots
Noeud de potence
Incorporate into other bottle cap projects -maybe the fish? bottle capPop top chain mail
Berkeley braid Knot... Strong, good for fluorocarbon line, kinda tricky to tie, and personally only make 4 wraps instead on 8.