Can "Fling" target a Player?
The rules say (emphasis mine):

115.4. Some spells and abilities that refer to damage require “any target,” “another target,” “two
targets,” or similar rather than “target [something].” These targets may be creatures, players, or
planeswalkers. Other game objects, such as noncreature artifacts or spells, can’t be chosen.

So yes, if a spell says &quot;any target&quot;, a player will always be a legal choice (assuming no other cards currently in effect restrict whether players can be targets).