For use on a Sun team:
Tangrowth @ Big Root / Leftovers
Ability: Leaf Guard
EVs: 252 SpD / 252 HP / 4 SpA
Calm Nature
- Grassy Terrain / Hidden Power [Fire]
- Giga Drain
- Leech Seed
- Ingrain / Synthesis
Grassy Terrain / HP Fire - I DO know that Grassy Terrain heals the other team to, but the 50% boost to Grass type (STAB in this case) moves helps a lot. HP Fire is for coverage and gets boosted by the sun.
Giga Drain - STAB, also more healing
Leech Seed - I like this for wearing down, also for even more heals
Ingrain / Synthesis - Again, your choice, but I prefer Synthesis for even MORE healing! Some people playing X / Y may not have access to Tangrowth getting Synthesis. This is due to no move tutors to teach him the move. However, Ingrain works just as well, if not better. Although you can't planning to be switching a lot.