Shell Break would be nice, but it still would have problems with Skarmory, other Grass-types, and Bronzong (amongst other things). Rock Head would have been amazing for Wood Hammer, imagine Shell Break + Rock Head Wood Hammer D:. But it's pointless to discuss these things that aren't real.
Torterra @ Leftovers
Ability: Overgrow
Nature: Impish
EV: 252 HP / 36 Def / 220 SpD
- Wood Hammer
- Earthquake
- Synthesis
- Stealth Rock
394/280/261 defenses are pretty nice. In the sun it gains a resistance to Water and Synthesis becomes a viable form of recovery. It's unique for sun teams because it provides crucial resistances to Ground and Rock, while also being able to switch into Tyranitar and Hippowdon. I used to be running Swampert with EQ/SR/Roar/Ice Beam, but Torterra has a few worthwhile advantages. First of all, it resists Ground and has access to Synthesis. Secondly, it has a lot more physical bulk than Swampert (95/105 defense vs. 100/90; 394/339 vs. 404/306 when fully invested). This allows Torterra to invest in special defense while retaining good physical bulk. Swampert can never reach the overall defense of Torterra. Torterra wasn't surviving powerful Fire attacks anyway (Hihidaruma CB Flare Blitz, Heatran Fire Blast, etc) so the sun doesn't hurt it too much in that respect. Access to Stealth Rock is nice on a sun team, so it's a necessity. I run this alongside Flash Fire Heatran and it works quite well. In the sun Torterra can counter stuff like Gyarados, resisting Waterfall, Stone Edge, and Earthquake, which is cool :D.