There's a rumour I heard a couple of years ago about Daddy Long-Legs spiders (see below re the name having different meanings in different places) having the strongest poison (or probably more correctly venom) of any spider, but that they don't have strong enough jaws (or long enough fangs, or ...) to bite humans.
Ricky Gervais has
a comedy bit about this, except he applies it to flies, not spiders. It's pretty funny, regardless.
This confusion is because in Ireland and the UK, a Daddy Long-Legs is a fly (in the US, known as a Crane Fly), whereas in the US it is used to refer to a kind of spider. Well, sort of.
According to
an article about the Daddy Long Legs Myth at UC Davis the term Daddy Long Legs refers not in fact to a true spider but to opilionids (see the UC Davis article for more detail; incidentally, there's very common ones in Ireland) but is often used to refer also to spiders. The article also firmly calls the venom/poison rumour out as myth.
Snopes agrees, but their source is the UC Davis page, so that doesn't really add much.