With Rain yeah, you usually have Ludi + Toed, then a third Surfspam in Kingdra, Kabutops (Rock Slide / physical mon), or Jellicent (options include Water Spout, Water Absorb, and Trick Room).
Scizor is pretty much mandatory, with Feint busting Guards/Protect, Bullet Punch for Whimsicott and Terrakion / general softening, and Bug Bite (maybe Aerial Ace for range) to break Ludicolo, Cress, and Musharna.
Gastrodon is available for TR rainspam.
After that, enjoy two team slots. Raichu offers fast Fake Out, Feint, Lightningrod, and manual Rain as support. Thunderbolt is pretty good too. Standard supports like Hitmontop work fine in Rain as well.
Tornadus and Thundurus specifically offer Prankster Rain Dance; Tornadus spams a powerful, ranged Hurricane while offering Tailwind as an option too, Thundy spams Thunder with t-wave as an option. Dragonite offers immense bulk, Hurricane + Thunder, Tailwind, Extremespeed, and a pretty sizable list on its own, and is an often-neglected choice in Rain teams. MegaMence being banned is another huge thing.
As for Sun, Rain Dance Thundy goes literal miles.