Bounce, Dragon Breath, and Effect Spore would also have the chance to paralyze, if I'm not mistaken. While these would be threats in-game, if Sceptile does make it to OU, then I think only Jirachi bothers with Body Slam, and Gyarados or Politoed bother with Bounce, but each of those cases are fairly uncommon, as far as I've seen. Aside from that, Synchronize would only paralyze through Dragon Breath or Body Slam, which is a Gen III tutor, and Static or Effect Spore? No.Nope, neither Grass typing or Lightning Rod actually prevents Paralysis, only the means of getting inflicted through Stun Spore or Thunder Wave, respectively. The only ways Mega Sceptile could get paralyzed is through Body Slam, Static, and Synchronize. Mold Breaker also goes through LRod but I don't know if any electric types get it.
Edit: Mega Ampharos gets Mold Breaker, oops.