Methyl cyanoformate is the organic compound with the formula CHOC(O)CN.  It is used as a reagent in organic synthesis as a source of the methoxycarbonyl group, in which context it is also known as Manders reagent.  When a lithium enolate is generated in diethyl ether or methyl t-butyl ether, treatment with Manders reagent will selectively afford the C-acylation product.  Thus, for enolate acylation reactions in which C- vs. O-selectivity is a concern, methyl cyanoformate is often used in place of more common acylation reagent like methyl chloroformate.
Methyl cyanoformate is also an ingredient in Zyklon A. It has lachrymatory effects.