Old thread, but I might as well contribute.
RBY
Slowbro
~ Reflect
~ Amnesia
~ Surf
~ Rest
We are all familiar with TobyBro right? This is TobyBro that lost TWave for Reflect! Amnesia doubles Special (+2 SpA / +2 SpD), making Slowbro rather impenetrable from the special side, outside of the frequent Thunderbolt crits :( It has great physical bulk and resistance to Psychic moves to start setting up. Many players neutered Slowbro with Explosion; iirc it's 340 move in RBY, and unlike in DPP and BW your slower Pokemon's turn ends after Explosion, allowing the opponent to finish off Slowbro with a second hit from a different Pokemon. With Reflect, however, Slowbro is guarded from Explosions and Self-Destruct, making it nigh invincible to take out without a crit :) This Slowbro is especially fierce mid- late-game when the opposing team is sufficiently paralyzed (you esp. want Chansey paralyzed, as 999 Special Slowbro barely misses a 2HKO on her).
There's a version of this that I've used to great results before.
RBY
Slowbro
~ Psychic
~ Withdraw
~ Amnesia
~ Rest
Yes, that's Withdraw.
Okay, first off is the STAB choice. Surf has more base power and more PP, I know. But you don't have Thunder Wave to break through Chansey and Starmie, so the 30% chance of Special-falls (in RBY) can save your neck. The super-effective hit on Gengar and Victreebel is also a really big deal, since both of those are dire threats to Slowbro with Thunderbolt and Razor Leaf respectively. You lose the SE hit on Rhydon and Golem, and the neutral hit on Jynx and Zam. Jynx isn't laying a finger on Slowbro anyway so that's not a big deal, Zam is a bigger problem but we'll come back to that one, as well as Rhydon/Golem.
Withdraw is a crappy move, but it's useful for this set for a couple of reasons:
1) +Def on Slowbro is nice given that Explosion's a really predictable answer to it, and Tauros and Rhydon/Golem love to pound on it when it's asleep. This is why you don't need Surf's SE hit against Rhydon - with a single Withdraw up, it won't even 4HKO without a crit and you can set up on it.
2) Withdraw has 64 PP. This may not sound particularly relevant in RBY, but Slowbro, particularly +Def Slowbro, forces stall wars an awful lot. Withdraw allows you to use Slowbro as an anti-setup setup, because you can bring it in, set up alongside your opponent, and then stall them out of their recovery move so you can KO them. That you're left with a 999 Defense, 999 Special Slowbro afterwards is what we call "icing on the cake". Withdraw Slowbro is also capable of stalling Zam out of Recover, allowing you to beat it that way if you can't get it paralysed beforehand (if it's paralysed, you're probably better off just smashing its face in with Psychic Special-falls).
The main downside of this set is that you're giving up T-wave - this makes Slowbro even more of an all-or-nothing gambit, since TobyBro will usually at least paralyse Starmie or Tauros before going down and give the rest of your team an advantage there. It likes a lot of paralysis support from teammates - specifically it wants Zam and Chansey paralysed (Yes! I did just tell you to paralyse Chansey!), and preferably Lax and Egg as well (so that you can throw up Withdraw before they Explode). Paralysing Starmie or Tauros is obviously great news, but good luck with that; this Bro handles Tauros fairly well anyway and your best bet on Mie is probably to blow up your own Egg or Lax on it. If they have Victreebel, do anything you possibly can to paralyse it before Slowbro comes out; Psychic Bro isn't fully countered, but Razor Leaf still hurts like hell. Same goes for Electrics if they have them, though killing them is preferable. Gengar's not a big issue because of Psychic's SE hit, but paralysis is still nice to avoid that one-in-five chance of Gengar popping in and immediately critting Thunderbolt for an OHKO.
Really, this thing does best when you build an entire team around it like I did, but when you can get it to shine, it's a superstar.