Fusion shots are when two slugs match together and make sort of a Yin Yang form. First, the the two slugs rotate around each other creating a vortex, Second, the vortex implodes, unleashing a pure fusion of both slug's greatest powers.
In episode eight of season two "The Unbeatable Master" the master used an Inkdevil slug with a Sonikin slug to make a Fusion Shot.
In episode eight of season two "The Unbeatable Master" Eli uses Joules and Burpy to make a Fusion Shot against Dr. Blakk.There are only three fusion shot seen 1 burpy and joules 2 sonikin and inkdevil 3 inkdevil and hoprock.