Which special characters can be used in your password?

Title says it all

By "special characters" do you mean punctuation ($%^&*(,.' or the sort of special characters you need to enter using a 3-digit code (at least on US/American keyboards)?

If it's the first, I'm pretty sure you can use them all (and, as far as I know, using any is quite enough to make brute-forcing your password impractical for anyone but the government or similar overpowered entities).

As for the second, I think they were at the basis of the "fort knox security" account-locking mechanism, meaning you could put them in your password when changing it, but then you couldn't enter them when logging in. Web interface has changed since then so I don't know whether that's still true. Be sure you have access to your e-mail (for a password reset) before you start experimenting with those.

I can confirm using normal keyboard symbols in PWs.

The latter I would assume are the ones no one knows how to make directly on a US keyboard and can't actually be physically typed. Like this: (ノಠ益ಠノ彡┻━┻

Could just use KeePass' password generator.

[...] 益 [...]

Is it me, or does that look like while wearing a villain mask ...