Paw graph

The paw graph is a triangle with one pendant edge.

The paw graph $H$ has $R(H)=7$. A colouring of $K_6$ with two disjoint red triangles and all cross-edges blue avoids a monochromatic paw. In $K_7$, a monochromatic triangle exists; avoiding a paw forces all its edges to the other four vertices into the opposite colour, which then forces those four internal edges into the triangle's colour and creates a paw.