Dog toys! I have several knit dog toy patterns that I am planning to convert to crochet because I think they will work better in crochet. For instance, I have a pattern for a knit ball that Pico
adores but I think would hold up much better in crochet (not to mention that I could crochet it in rounds instead of rows and avoid having to sew a seam!) And the same goes for the knit bone toy - it's much easier to crochet 2 bone shapes and sew them together than knit them.
Also, I have a pattern where you knit a really long I-cord (about a half-ball of yarn worth) and then twist it together until it doubles back on itself twice. You tie an overhand knot on each end to form a bone shape. It's kind of like the knotted rope bones you can buy but it doesn't shred as much. I was thinking i t would work well with a really long piece of single or double crochet (great kids project too.)
I'm thinking about a G-hook with worsted weight cotton.