关公

关羽, the Three Kingdoms general famed for his loyalty to 刘备, was later worshipped all over China as 关帝. He is shown with a red face, a long beard and a long-bladed halberd. Shops and restaurants keep a small shrine to him as the god of wealth, and police and secret societies alike honour him as the god of loyalty.

关公面前耍大刀, 'to swing a big sword in front of Lord Guan', means to show off in front of a master, like 班门弄斧. People often say it of themselves, out of modesty.