Often writers use symbols from the animal kingdom to symbolize courage, and this is something mankind has done for many years. For example, lions might be used as such symbols, or various birds of prey, such as the falcon or the hawk. 

Various cultures and religions have their own symbols of courage, which could easily be used by writers. In Roman mythology, Mars was the God of war, and so I suppose the planet Mars could be used as in a poem or novel as a symbol of courage and aggression. In the Hindu religion, courage is represented by Hanuman, a monkey and a general in Indian mythology.  In some African cultures, the leopard is a symbol of courage, and in astrology, Aries is a symbol of courage, too.

There are various parts of nature that might be used symbolically to indicate courage either metaphorically or literally.  One example might be a mountain that requires courage to climb.  Another might be a raging river that someone must navigate.  Generally,  the conquering of nature is a sign of courage, endurance, and strength.

I do not play any video games, but it would be interesting to know what kinds of symbols of courage appear in these.  My guess is that many such symbols are based in mythology.  What kinds of symbols of courage have you seen in movies or on television.  I don't think the symbols of courage in various media are likely to vary all that much. 

An excellent book on signs and symbols is The Illustrated Book of Signs & Symbols, by Miranda Bruce-Mitford, published in 1996 by DK Publishing Company.  It is fascinating to see what signs and symbols have been used by different groups over thousands of years.