The only way I'm able to judge an unit "surprisingly good" is when I have problems breaking it...

For me the grand-champions are African Elite Pikemen. IA Karth-Hadasht fields huge numbers of them and when playing Ptollies I often see them inflicting huge losses to my Agema Klerouchon (attacking from the front) and Tindanotae (attacking from the rear). Tough nuts to crack...