Murkrow is probably going to be doing the Electrode niche all over again...
That said, it's a choice between Damp Rock or Eviolite on Murkrow. However, with Politoed in OU and the existence of Obamasnow, Vulpix and Hippopotas, rain seems to be taking a backseat. Kingdra can easily lolpwn Hippopotas though, and it shouldn't be that hard to OHKO Vulpix with Hydro Pump, even with Sun.
Most of the best rain abusers are now UU, the only people missing are Starmie, Vaporeon and Toxicroak. This should be fun.