Muggle who complimented Tom Riddle in 1981

"Nice costume, Mister!"

- Muggle boy to Voldemort

This Muggle boy complimented Lord Voldemort for his "nice Hallowe'en costume" in October 31, 1981, moments before Voldemort killed James and Lily Potter in their house in Godric's Hollow. Voldemort thought about killing the child, but ultimately deemed the act "unnecessary". The incident was discovered by Harry Potter through an inadvertent mind-reading.

Behind the scenes
Voldemort's reasoning for sparing the child's life was not made clear, though it can be surmised that Voldemort had chosen not to use magic until he had arrived at the Potter's house in case his presence was detected by any spies. Another possibility is that Voldemort simply thought the child was not worth his time or effort.