Nose plug has always been my go-to RC, and the finger count is usually fairly reliable as well (interestingly I find with this one, if I;m dreaming it will be difficult to determine how many fingers I have).

Generally though, with reality checks, they are mostly useful for when you think you might be dreaming. The act of becoming lucid isn't in the reality check, that's just to reassure yourself. You become lucid when you actually suspect that something's off. When you think about it, you constantly excuse things as weird as having 6 fingers in your dreams.