Onyx Tanuki
Ma! There's a weird 'nuki in the yahd!
A few more RU/NU ideas...
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Walrein @ Leftovers/Icy Rock
Ice Body/Oblivious
Modest
252 HP, 252 SpAtt, 4 SpDef
- Substitute
- Hail/Aqua Ring/Encore
- Frost Breath/Signal Beam
- Surf/Water Pulse
Oh, poor Walrein. You have the stats to be a great bulky special attacker, but your special movepool is such absolute utter garbage. You have the movepool to be a great physical attacker, if only your Attack wasn't mediocre that you pretty much were forced to run a Bulk Up or Belly Drum set just to compete. Still, he has his uses, particularly in Hail teams. First off, I've maxed his HP and SpAtt, and put the excess in his SpDef, and his Modest nature ensures he hits hard with what little he does have to attack with. The item choice depends on if you plan on having him set up Hail for your team, but he's more than likely better off with Leftovers, and give the Icy Rock to your Abomasnow (or Aurorus if its hidden ability becomes available). Ice Body works for additional recovery in a Hail team, but Oblivious is nice too since it keeps Walrein from being Taunted. Just don't give it Thick Fat unless you really don't want it to not resist Fire, because it's already double-resistant to Ice and neutral to Fire, making it decent enough as a switch-in on either. Substitute is pretty obvious; his bulk is great enough that his Subs can't be killed by a Seismic Toss, and unless he's tanking Super-Effective hits, he could potentially recover what he spent to put the Sub up in the first place. The second slot goes to Hail if he's going to be used to set it up, or else he can set up Aqua Ring to max his health regen or Encore to help him shut down setups and encourage a switch which would allow him to set up a Sub. As for attacks, his Water STAB is really limited to just Surf and Water Pulse, the former being the stronger while the latter has a chance to confuse. Frost Breath is the Ice STAB of choice, allowing Walrein to break through SpDef boosts since it's auto-crit, but if you want to, you can sacrifice it for Signal Beam to improve Walrein's coverage, since Water/Bug isn't too shabby in that regard.
I think one of Walrein's biggest draws will be its HP recovery. Assuming it has Ice Body and runs Aqua Ring and Lefties, it could get up to 3/16ths back. That's nearly enough to fully recharge what was spent to set up a Sub. However, he's definitely not one of the top-level threats due to his meh coverage, meh typing, meh offenses, and how vulnerable he is to being phased out (which would cancel out both his Sub and Aqua Ring). If he's not in Hail, I'd honestly not even bother running recovery and just go Encore. You could also go the stall route, in which case you could keep Frost Breath and drop his Water STAB in place of Toxic.
Wormadam-S @ Leftovers
Overcoat
Sassy
252 HP, 4 Def, 252 SpDef
- Infestation/Stealth Rock
- Toxic
- Substitute
- Rest/Gyro Ball
At first glance Trash Coat Wormadam seems like a bargain bin version of Forretress, but it really works more like an alternative to Shuckle. It's got amazing defensive typing combined with Overcoat (though in its case that only blocks Spore and prevents Hail damage) and access to a rather varied movepool. It unfortunately doesn't especially hold up since it's got lower stats in pretty much everything to the point that its movepool is rendered rather useless. However, since its defenses are even, it can choose to split them or focus on one or the other. Personally I'd go for special just to throw people off who expect it to be up against Dollar Store Forretress. Sadly, its lack of Rapid Spin and lacking offenses pretty much relegate it to pure stall or Toxic spreader. Substitute and Toxic are needed, with the former blocking Will-O-Wisps and the latter being Wormadam's primary damage source. From there, Infestation could be used to stall the foe out, or Stealth Rock to punish them for trying to keep the Toxic damage down. Rest works to heal off Substitute damage as well as take away status if Wormadam doesn't Sub up on time, while Gyro Ball provides it some offensive presense to keep it from being Taunt bait. Lefties obviously for recovery, though one could run Chesto Berry if they're running Rest or Occa Berry in the event that the foe has a Fire move packed away somewhere.
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Walrein @ Leftovers/Icy Rock
Ice Body/Oblivious
Modest
252 HP, 252 SpAtt, 4 SpDef
- Substitute
- Hail/Aqua Ring/Encore
- Frost Breath/Signal Beam
- Surf/Water Pulse
Oh, poor Walrein. You have the stats to be a great bulky special attacker, but your special movepool is such absolute utter garbage. You have the movepool to be a great physical attacker, if only your Attack wasn't mediocre that you pretty much were forced to run a Bulk Up or Belly Drum set just to compete. Still, he has his uses, particularly in Hail teams. First off, I've maxed his HP and SpAtt, and put the excess in his SpDef, and his Modest nature ensures he hits hard with what little he does have to attack with. The item choice depends on if you plan on having him set up Hail for your team, but he's more than likely better off with Leftovers, and give the Icy Rock to your Abomasnow (or Aurorus if its hidden ability becomes available). Ice Body works for additional recovery in a Hail team, but Oblivious is nice too since it keeps Walrein from being Taunted. Just don't give it Thick Fat unless you really don't want it to not resist Fire, because it's already double-resistant to Ice and neutral to Fire, making it decent enough as a switch-in on either. Substitute is pretty obvious; his bulk is great enough that his Subs can't be killed by a Seismic Toss, and unless he's tanking Super-Effective hits, he could potentially recover what he spent to put the Sub up in the first place. The second slot goes to Hail if he's going to be used to set it up, or else he can set up Aqua Ring to max his health regen or Encore to help him shut down setups and encourage a switch which would allow him to set up a Sub. As for attacks, his Water STAB is really limited to just Surf and Water Pulse, the former being the stronger while the latter has a chance to confuse. Frost Breath is the Ice STAB of choice, allowing Walrein to break through SpDef boosts since it's auto-crit, but if you want to, you can sacrifice it for Signal Beam to improve Walrein's coverage, since Water/Bug isn't too shabby in that regard.
I think one of Walrein's biggest draws will be its HP recovery. Assuming it has Ice Body and runs Aqua Ring and Lefties, it could get up to 3/16ths back. That's nearly enough to fully recharge what was spent to set up a Sub. However, he's definitely not one of the top-level threats due to his meh coverage, meh typing, meh offenses, and how vulnerable he is to being phased out (which would cancel out both his Sub and Aqua Ring). If he's not in Hail, I'd honestly not even bother running recovery and just go Encore. You could also go the stall route, in which case you could keep Frost Breath and drop his Water STAB in place of Toxic.

Wormadam-S @ Leftovers
Overcoat
Sassy
252 HP, 4 Def, 252 SpDef
- Infestation/Stealth Rock
- Toxic
- Substitute
- Rest/Gyro Ball
At first glance Trash Coat Wormadam seems like a bargain bin version of Forretress, but it really works more like an alternative to Shuckle. It's got amazing defensive typing combined with Overcoat (though in its case that only blocks Spore and prevents Hail damage) and access to a rather varied movepool. It unfortunately doesn't especially hold up since it's got lower stats in pretty much everything to the point that its movepool is rendered rather useless. However, since its defenses are even, it can choose to split them or focus on one or the other. Personally I'd go for special just to throw people off who expect it to be up against Dollar Store Forretress. Sadly, its lack of Rapid Spin and lacking offenses pretty much relegate it to pure stall or Toxic spreader. Substitute and Toxic are needed, with the former blocking Will-O-Wisps and the latter being Wormadam's primary damage source. From there, Infestation could be used to stall the foe out, or Stealth Rock to punish them for trying to keep the Toxic damage down. Rest works to heal off Substitute damage as well as take away status if Wormadam doesn't Sub up on time, while Gyro Ball provides it some offensive presense to keep it from being Taunt bait. Lefties obviously for recovery, though one could run Chesto Berry if they're running Rest or Occa Berry in the event that the foe has a Fire move packed away somewhere.