Tyranids have a heap of new options when it comes to throwing out the pain and suffering in the shooting phase. The previous codex simply did not have enough punch to stop vehicles reliably with guns. That is no longer the case, and you can bring a significant shooting game to the table. I'll go into my thoughts on the major ranged combat options in the book, and possible support units for them. And, they're all lovely Assault weapons, so you can pop shots AND move and fistfight, should you want to do so.
By 'major' ranged stuff, I'm talking about a unit that's actually focused on shooting, as opposed to something like a Trygon or Tervigon, which simply has the option to make ranged attacks.
Common Shooting Options
There are a couple of ranged weapons that several creatures share, and that you can use to bust armor. These guns are:
Heavy Venom Cannon: 36" S9, AP4, Small Blast, -1 on Vehicle Damage Chart against closed-top
Stranglethorn Cannon: 36" S6, AP5, Large Blast, Pinning
Devourer w/ Brainleech Worms: 18" 6 shots S6, AP-, -1 to morale checks from shooting if they inflict an unsaved wound
Cluster Spines: 18", S5, AP-, Large Blast
Stinger Salvo: 18", S5, AP4, 4 shots
Thorax Swarms: Template, with profile:
-Electroshock beetles, S5 AP5
-Desiccator Larvae: S1, AP-, wounds on 2+
-Shreddershard Beetles: S3, AP-, Rending
This is the basic monstrous creature menu for guns. The Heavy Venom Cannon is your main support option, as it's passable against infantry and capable of inconveniencing vehicles. It's not so hot for killing armor, but can at least damage it.
The Stranglethorn cannon is usually an option alongside the Heavy Venom cannon. S6 harms its effectiveness against vehicles, but it's still a fine way to inflict wounds on footsloggers.
The Brainleech-packing Devourer is the good old high-rate-of-fire monstrous creature gun. You want infantry and monstrous creatures to eat it? This is how you feed them.
The Stinger Salvo is a backup gun for larger monstrous creatures, and can usually be exchanged for Cluster Spines. Given the BS3 on most of the creatures that can get these, I'm inclined to go with the spines for the large blast template, unless you really want to use S5 for anti-vehicle work (...which might scare AV10 a little) or think you can't get more than two hits average on the blast weapon.
The Thorax Swarm is another one of those backup weapons on larger monstrous creatures. It comes with the S5, AP5 shot, and costs points to upgrade. Frankly, I'd rather spend the points on other things. I consider it a point-defense system; if you have to use it things have probably gone downhill, or you're already winning.
The Weapons Platforms
The Hive Tyrant
The first decision you need to make is whether you want winged or walking. The Hive Tyrant's abilities are support-oriented, and put on a nasty chassis. If you're going to bring guns on it, though, here are the thoughts:
1) Winged Tyrant w/ 2x TL Devourers 
This is a bit of a 'classic' loadout. It's purely short-ranged shooty; a dozen TL shots at S6, BS3 means an average of 9 hits, and 8-9 wounds on infantry. You still have decent assaulty capabilities, too. This is really the multi-role tyrant, though it costs you a hefty 260 points. You can drop 15 off the price and keep the whip/sword combo if you want, but that dilutes you a bit more, and you might just consider wings and melee.
2) Walking Tyrant w/ TL Devs, Heavy Venom Cannon [210 + vet abilities + Tyrant Guard]
This is the basic multi-role walking tyrant. You will want to pay another 120 for a couple of Tyrant Guard, just to keep you alive longer. You can inconvenience vehicles, and scare infantry. Drop 10 points to go double-devourers, but expect to spend some time running. Additionally, pick up the non-shooting powers for your support stuff.
Honestly, this is one of my favorite additions on paper. It's a fast attack choice that's basically a flying gun. It starts with a Stranglethorn Cannon and Stinger Salvo, though I would promptly upgrade to the Heavy Venom Cannon and Cluster Spines. 170 points for instant duality; you can harass vehicles at a safe distance, or harm enemy infantry that get in close. In a pinch, you can go punh something.
The downside is of course durability, so prepare to bring a pair of harpies and some other monstrous creatures. Still, I think it's a strong addition to an MC-heavy list, and its durability just begs more questions about target priority.
Say hello to the red-headed stepchild of the codex. It got a hefty cost increase, lost its ability to be taken in the elite slots (...which is not actually a bad thing), but can come in broods of 1-3. So, what can you get on the Carnifex for guns?
About the same as the tyrant. You get one big gun, and a choice between Deathspitters and Devourers. The problem is that if you want big guns and anti-tank on the Carnifex, you have the shootiness of the tyrant and close to the cost of the Tyrannofex, but you don't have the Tyrant's support capabilites or the Tyrannofex's sheer firepower.
Frankly, I'd skip the Carnifex as a gun platform unless you were just totally opposed to the Tyrannofex. The Carnifex with Venom Cannon and TL Devourers costs 200 points; the Tyrannofex with Rupture Cannon costs 265, and I can tell you that those 65 points make a HUGE difference.
The Purpose-Built Gun Beasts
In addition to our more versatile monsters, we have three guns that are bodies, more or less: the Zoanthrope, the Hive Guard, and the Tyrannofex.
Ah, the Zoey. They come in broods of 1-3, and have two guns:
-S10, AP1 Lance at 18"
-S5, AP3 Small Blast at 24"
Scary, yes? We have duality. The downside is that we are a huge target; T4 with a 5+/3++ and two wounds makes you worry about S8 weapons, and people will do their level best to gun these things down, because they ARE that lethal. Frankly, a full brood of these should be able to maim/nuke just about any armor in a single round, and can put the hurt on infantry, two.
The achilles heel? Gotta pass those psychic tests. People that bring psychic tests can put the hurt on the Zoanthropes.
T6, 4+, two wounds, and a, S8 AP4 Assault 2 24" gun that doesn't care about LOS. Compared to the Zoanthrope (its fellow elite), you're trading some graphic firepower for reliability. You only get cover against the Hive Guard if you're in or touching terrain, as well. This means you can slap Hive Guard behind a wall, pull the trigger, and the enemy might not be able to see you to shoot back.
The downside is of course the short range, and like the Zoanthrope you can get sorted in melee without that much of a problem. On the bright side, your T6 means it takes some serious firepower or specialist kit to drop you.
Anyone like S10 guns? You DO? What about an S10, AP4, Assault 2 gun with a 48" range that can't be blown off the carrier? Are you willing to pay a bit for it? Then the Tyrannofex is your buddy. 265 points nets you a monstrous creature with T6, 2+ armor, six wounds, and a BS3 to go with the Rupture Cannon, Cluster Spines, and the basic thorax swarm. Screen it well (since it can't fistfight worth a darn, and anyone with a hidden powerfist can eventually grind it down...) and it will do wonders for you.
Supporting Your Guns
As your guns are not vehicles, they can be tied up in assault. As such, you will want to consider little gribblies as shield, but be aware that they can still get tank-shocked through.
The other issue with our guns? Some of them are shorter-ranged. See the Hive Guard and Zoanthropes in particular, but don't overlook the Devourer-wielding nuts, either. How to fix this? Consider the Tervigon: Onslaught lets you run AND shoot. Get an extra d6 of movement, and you might get range a little sooner. As an extra benefit, the Tervigon can ALSO produce meat shields for your guns.
The Zoanthrope can take a Mycetic Spore and guarantee the chance to shoot, but this entails building in reserves manipulation (IE: at least one Hive Tyrant) and may not see them arrive when you need them, or where you need them. But, it IS an option.
1) Hive Tyrants are support units for your army, but can take decent shooting.
2) Harpies are a solid support element with the Heavy Venom Cannon and have some versatility, you're certainly committing to bringing multiple MCs.
3) Carnifexes...skip them for shooting. Tyrant has similar capabilities and support options; Tyrannofexes are simply superior for popping vehicles.
4) Zoanthropes are graphically destructive, but have short range and are vulnerable to psychic defenses
5) Hive Guard are solid performers, but still short-ranged
6) Tyrannofexes are flat-out dangerous, but require support and have some accuracy issues.
7) Tervigons can help you with that 'range' problem with Onslaught
The Opinion Side
Frankly, I'm planning on converting Hive Guard from Warriors. I'm also planning on converting Tyrannofexes from Carnifex kits; one of those is actually WIP. I will post pictures. So far the thought is to make the Tyrannofex look like a larger hive guard, using some spare carapace bits and the like.
I think that the Hive Guard and Tyrannofex make a good team; one hunts lighter armor and the other can nail any armor value out there (...unless your dice decide you can't hit). I'm looking at running 3x2 Tyrant Guard and at least two Tyrannofexes, with Tervigons as support.
I'd like to say I'm original, but I think this is just going to be a solid kind of build for the bugs. Part of me wants to roll it with double winged tyrants, or fit some Shrikes in there, though.