Pokémon:
- Voltorb (Level 21): Electric
- Pikachu (Level 18): Electric
- Raichu (Level 24): Electric
Weaknesses:
All of Lt. Surge's Pokémon are Electric-types, making them exclusively weak to Ground-type moves. Electric-type moves have no effect on Ground-type Pokémon.
Strategy:
Your best bet for this Gym is a strong Ground-type Pokémon. You can catch a Diglett in Diglett's Cave (east of Vermilion City) and train it until it evolves into Dugtrio, or use a Sandshrew/Sandslash (found on Route 3). Teach them Ground-type moves like 'Dig' or 'Magnitude' (if available via TM).
Ground-type Pokémon will be immune to Lt. Surge's Electric attacks and deal super effective damage in return. Be cautious of Raichu's 'Mega Punch' or 'Mega Kick' if your Ground-type is also weak to Fighting. Keep your Ground-type healthy and unleash powerful Ground attacks.
Reward:
Thunder Badge, TM24 (Thunderbolt)