I've heard of two accounts of this happening. One was in Harry Järv's memoirs, where a Russian sniper regularly fires from a tree at a Finnish outpost. Framom främsta linjen/Etulinjan edessä is based on Järv's memoirs.
The other one is Carwood Lipton in Band of Brothers. According to this Lipton climbed a tree to fire upon some Germans. Might not be 100% accurate, though. BoB seems to have its fair share of inaccuracies. Supposedly, this is based on Winter's memoirs.