The Nissin Air10s is a wireless flash controller that provides TTL and HSS support between camera brands.
Millman Tso reviews the Kenro Speedflash KFL101, a flash designed to work with both Canon and Nikon cameras. Is it any good?
The $120 Yongnuo Speedlite YN600EX-RT II has Canon RT radio control and supports both Canon and Nikon's optical wireless TTL systems.
Is it a studio light? Is it a speedlite? Francesco Rizzato reviews the Bresser SJS-200, a hybrid bare-bulb flash with HSS.
Adorama's Orlit Rovelight RT-610 is a TTL/HSS battery monolight compatible with Canon's RT flash triggers.