Icy Wind: DISALLOW
I think people are seriously underestimating the power of Icy Wind, and I'm not just talking about damage (although in reality, people are underestimating damage outputs too). When you have a move that can theoretically 2HKO your main counters, that is not good. Thundurus cannot switch in anymore. Many people in this thread have claimed that Tomohawk cannot stay in on Thundurus after an Icy Wind...but do you realize that Thundurus is at -1 Speed? And Icy wind does 45%-51% damage to it? After SR, that is a guaranteed 2HKO on one of Tomohawk's greatest counters. Similar things can be said for Zapdos. The -1 Speed really takes its toll on a lot of things, as it's possible to 2HKO a lot of things without even taking an ounce of damage. There's a reason why Tomohawk has average speed: so that it can be countered by certain threats. Icy Wind takes away those threats.
Furthermore, there is almost no difference between the damage output of Icy Wind and HP Ice, so saying that "it's a weaker HP Ice" isn't a great reason. It's a measly 15 BP off - even less than the difference between Flamethrower and Fire Blast. It only misses out on one KO (Garchomp), which HP Ice doesn't even guarantee! It doesn't lose any other OHKO's or important 2HKO's as a loss of power. It really is that powerful, yes. It should be disallowed.
Hurricane: ON THE FENCE
Hurricane is an interesting topic. There's a few issues I have with it that gives it my full support. I am not quick to throw out the possibility of a Scarf or Specs set combined with Rain support, which would not only give it access to a 120 STAB BP move with no drawbacks, but also give it the opportunity to OHKO Tyranitar with a reliable STAB move. That is something Tornadus cannot do. It also has better overall bulk than Tornadus with a good defensive typing and Intimidate. A Scarf/Specs set will definitely be considered, and may be extremely good.
However, Rain also brings out Tornadus, Thundurus, and Zapdos. Which all pretty much screw over Tomohawk in Rain. So, it's not like it's unstoppable. Outside of Rain, we still have that terrible 70% accuracy that is quite annoying to rely on. In regards to Steels switching in and getting hit with another move, I agree with Korski in that Fighting STAB is pretty powerful combined with Hurricane. However, Fire moves are somewhat of a moot point, since either Rain will be running, or you have access to a Focus Blast-esque move that will miss because you want to have a Fire move on your movepool. Overall, I think I will support this move, but I am still wary of the consequences.
Disagree on the egg move, though. I don't think it's that powerful nor controversial enough to warrant such a thing. Besides, you can only go so far with move combinations (ie: egg move Aura Sphere all you want, this thing will get the TM for Focus Blast).
Flamethrower / Heat Wave: ALLOW
Mostly redundant coverage with Fighting. I don't think it will be used much, since it causes a lot of 4MSS plus limits Tomohawk's options, but it's still useful enough to be considered on a movepool. Both should be allowed. Not like there's really enough of a difference between the two to warrant an exclusion of one.
Grass Knot: ALLOW
I agree wholeheartedly with capefeather. It allows us to hit bulky Waters for good damage, but still allows us to have Rotom-W counter us. It's a perfect fit..
Water Moves (Surf / Muddy Water / Scald): DISALLOW
I don't see why we should be giving yet another tool for Tomohawk to use on a Rain team. It doesn't make much sense to give this thing any Water move, flavor or not. It's also a great neutral attack on things that resist Tomohawk's STABs, including 2HKO'ing Zapdos and Thundurus. I'm going to have to say no to this.
Volt Switch: ON THE FENCE
I understand that Gyarados is rising in usage, but is a OHKO with an Electric move on a 4x weak Pokemon really causing this much of a scare? I think we've lost sight of what the move will really be used for, and that is scouting and switching. I feel that, while unnecessary in most cases, Volt Switch shouldn't be disallowed. There's not really a huge reason to do so. Unless I'm missing some major calculation that will make this terrible (and to be honest, it's pretty much just using HP Electric), I don't see how this is OP'd or UP'd in any way. The reason I'm on the fence, however, is the popularity of such an unnecessary move, which might decide the outcomes of movepool battles way too much.
U-Turn: ALLOWED
Basically Volt Switch with no immunities but with almost no power.
Super Fang: DISALLOW
I think the problem with Super Fang is just how well it really does against Stall, especially with a Pokemon that has great bulk and a possible access to recovery. I'm all for shifting momentum, but being able to crush Stall so easily detracts from the purpose of the concept in my opinion.