Bows and arrows are what I remember from the Lag B’Omers of my childhood. None of this bonfire stuff.
There are three reasons for the bow and arrow.
1) As a reminder of Bar Kochvah’s war against the Romans.
2) Because the Jews used to go out to the woods to learn Torah, but tricked the Romans (who forbade learning Torah) by telling them they were going hunting.
3) Because no rainbows appeared during the lifetime of Rabbi Shimon bar Yochai, and the Hebrew word for rainbow (keshet) is the same as the Hebrew word for bow.