I could see a Bulk Up set on Poliwrath work. It has to have some form of boosting it's Atk if it's planning on actually harming something, and Bulk Up seems to be a solid option for that, as it also increases it's endurance abilities, which are quite solid already due to it's slightly above average defenses.
Poliwrath @ Leftovers
Impish – 188 HP, 152 Def, 88 Speed, 80 SpDef
Water Absorb
~ Bulk Up
~ Brick Break
~ Waterfall
~ Rock Slide / Ice Punch
I love this set personally. It has enough Def to take 4 CB’d Stone Edges from Rhyperior, provided that the last three hit this thing after it has used Bulk Up once. It takes crap from all Tyranitar’s attacks. It can also take 2 Earthquakes from a CB Rhyperior, provided it has Bulked Up before they hit. I’d call that pretty amazing. This can come in on a lot of stuff. Not only does it pose a huge threat to Tyranitar (it OHKO’s max HP/some Def Tyranitar after 1 Bulk Up), it also lives through pretty much any of it’s attacks. The same goes for Rhyperior, except for Earthquake. The obvious choice would be to come in on a predicted Water attack of course, but this can actually come in on a lot more. After it may have forced a switch, and you’ve used Bulk Up on that turn, you can hurt a whole lot of things very badly. Just watch out for special attacks (it can still take on 2 Grass Knots from a neutral natured max SpAtk Manaphy/Starmie, although Starmie will most likely use Thunderbolt, which IS a 2HKO).
Hypnosis is better spent on a faster pokemon or something that can make very good use out of it, by using a +2 stat-boosting move on the turn your opponent withdraws their sleeping team member. Poliwrath already lacks said stat-boosting moves. Bulk Up works too slowly when used in conjunction with Hypnosis (you want to get the best out of that one turn of set up you get for using Hypnosis), so I'd rather not use the both of them on the same moveset. That, and the fact that you will only be able to use two different attacking moves hurts as well.
Hypnosis could still be a viable option on it, as Life Orb provides itself as a solid hold item (this resists Stealth Rock, so Life Orb isn't as suicidal on this as it is on most other pokemon) to boost the damage it does.
Poliwrath @ Life Orb
Adamant – 124 HP, 228 Atk, 68 Def, 88 Speed
Water Absorb
~ Brick Break
~ Hypnosis
~ Waterfall
~ Rock Slide / Ice Punch
With this spread, you can 2HKO an Impish max Def/min HP Rhyperior with Waterfall, while you’re also able to survive a Choice Banded Earthquake from his side. You’ll even have enough HP left to take one turn of recoil of Life Orb damage. It OHKO’s Tyranitar with great ease with Brick Break and it can still come in on quite some stuff thanks to Water Absorb. If you’re able to force a switch by coming in on something, you can use Hypnosis on the switch to force yet another switch, just to have a nice side-strategy to work with. Add in Stealth Rock support from another pokemon you had used and you have just dealt some nice damage to begin with. That’s just an option though. Again, Rock Slide and Ice Punch are both nice options.
Those are just some of the ideas I've had for this pokemon, I figured I'd share them with you.