Last time I was about to enter Rusturf Tunnel and beat Team Aqua. I was about to face the grunt when a wild Whismur popped and I decided to attack it with Ted. Surprisingly these are quite easy to kill and they are loaded with loads of experience points: killing 6 or 7 got Ted from Lv. 6 to 12! Ted was able to handle the grunt's Poochyena by itself and then take care of the trainers outside the tunnel.
As I arrived to Dewford, I knew Ted wouldn't help much against the Fighting gym. So I decided to train Greg and evolve it in Granite Cave. I expected to find a Geodude or Aron, but surprisingly I found a female Sableye I named Bijou. As soon as Bijou was added to the team, I realized how she was the perfect Pokémon to beat the gym. Being a ghost, she could easily handle Machops and Makuhitas and in no time I could show off the badge! I can't believe I never used a Sableye before, it's so useful!
Right now, I'm at Slateport, where Ted has just evolved into Loudred.