It’s strange how people often complain about their lack of opening knowledge when there are so many interesting sidelines in which it’s easy to be an expert. And when you mention such possibilities the usual reaction is that they can’t possibly be good, meaning that because there aren’t being played at super-GM level. This is why restaurants sit their first customers next to the windows.
The following game shows British Master John Littlewood using the so-called Larsen Variation of the Philidor (1.e4 e5 2.Nf3 d6 3.d4 exd4 4.Nxd4 g6) but Larsen didn’t play it much whereas Littlewood used it in literally hundreds of games. And he brought off some spectacular wins with it, such as the following one: