The first two links are from a public-domain pool of personality scales. Shorter versions of the Big Five are also available there. The original dark triad scale is free to use. I’m not exactly sure about the copyright status of items described in academic papers, but are presumably covered under fair use.
If this were to happen, here are some scales possibly worth including:
Big Five personality traits and aspects, 100 items
Need for order and perfectionism, 10 items each
Dark triad (Machiavellianism, narcissism, psychopathy), 12 items
ADHD (gated), 18 items
Grit, 8 items
There’s also much smaller Big Five tests—going as small as ten items.
Are those lists copyright free?
The first two links are from a public-domain pool of personality scales. Shorter versions of the Big Five are also available there. The original dark triad scale is free to use. I’m not exactly sure about the copyright status of items described in academic papers, but are presumably covered under fair use.