King's Rock and the Razor fang are not affected by Serene Grace, if the move already causes flinching.
For example, if a Togekiss used Air Slash, the odds of Air Slash flinching would be 60%, because Serene Grace doubles the odds a move's special effect occurring. The King's Rock and Razor Fang cause moves without a flinch chance traditionally to have a 10% chance of flinching the opponent.
However, as stated above, the King's Rock and Razor Fang are affected by Serene Grace, if the move doesn't already have a chance of flinching the opponent.
To use another example, lets just say a Togekiss runs a set with Heat Wave, King's Rock, and Serene Grace. There would be a 20% chance of flinching with heat wave, due to Serene Grace doubling the 10% flinch chance from the King's Rock.
Besides that, I cannot find any sources that state that other items are affected by Serene Grace.
All in all, The King's Rock and Razor Fang are only affected by Serene Grace when using a move that does not have a flinch chance normally.
Sources: This question and This.