Earliest brilliant move ever
 
    
  
  
   
    
  
  
  Chess.com: 1. e4 e5 2. Nc3 Bc5 3. Na4 Bxf2+!!
Wikipedia: 1. e4 e5 2. Nc3 Bc5 3. Na4?! Bxf2+!?
My opinion: 1. e4 e5 2. Nc3 Bc5 3. Na4? Bxf2+!
 
    
  
  
  Deflection to obtain a mating square. That's a high-level concept. But brilliant, no. Brilliancies should involve multiple-piece setups and ghost traps.
 
     
     
     
     
    