WAAAAAAAAAAAAAAGH!!!
Now that that's out of the way, let's check out our most basic Orks Troops Unit: Boyz.
WS 4, BS 2, S 3, T4, W 1, I 2, A 2, Ld 7, Sv 6+
Ork Boyz cost 6pts/model. A mob can have 10-30 Boyz (60-180 pts.) That's a very low point cost. You're looking at outnumbering a Marine army ~3:1 on average with a Troops choice like this. That's amazing. Toughness of 4 will help to keep the casualties down, despite the lack of real armor. WS 4 and A 2 are what should really be standing out to you. These guys are one of the best Close Combat units in the game, point-for-point.
Mob Rule
This allows you to (in case of a required Leadership Test) replace your Ld 7 with the number of Boyz still alive in your mob. This is great movitation for maximizing your mob to 30 Boyz. If 11 or more are still alive, the mob is Fearless!
Furious Charge
When your Boyz charge into assault, they get +1 S and +1 I for that first round. That would make the mob of up to 30 Orks hit with S 4. I hope you're never on the recieving end of this.
Waaagh!
Once per game, the Ork player can declare a Waaagh! during his Shooting Phase. All of his units with this rule get Fleet of Foot for the rest of the turn. Fleet of Foot!
... so, to sum up: You have a group of 30 Orks that can Fleet during a Waaagh!, hitting you 4 times/model (assuming Slugga/Choppa) with WS 4, S4 ... and they're Fearless until below half strength! And all for only 6 pts/model. THIS is why they are one of the best Close Combat units in the game.
Equipment
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Slugga/Choppa
This is their standard Pistol + Close Combat Weapon arrangement.
Shoota
Free replacement for the Slugga/Choppa, in case you want to go the shooty route with your Boyz. Shootas are 18" S4, AP6, Assault 2. Now, if you remember the Boyz' stat lines, you'll remember that their BS is only 2. That really sucks. However, Imagine 30 Shootas (60 shots) at S4 ... not as bad as before. In addition to this, if you do decide to assault someone, you're not completely at a loss without the Slugga/Choppa; you're only -1A per model. They're still hitting 3 times/model on the charge, and with all the other goodies mentioned above!
Big Shoota/Rokkit Launcha
For every ten Boyz in the mob, you can have one replace his gear for one of these. A Big Shoota is 5pts, and is 36" S5, AP5 Assault 3. This added range could help out a lot if your intention is to park this mob on a mid-field Objective, or even the longer-range Objectives. Rokkit Launchas are 10pts, and are 24" S8, AP3 Assault 1. Great power, decent range, but a low rate of fire for a BS2 model. Again, as before, enough of these are bound to off-set the high miss-rate ... but at 10pts/Rokkit Launcha, they'll burn up your points fast.
'Ard Boyz
One mob of Boyz per army can upgrade to 'Ard Boyz. This gives the mob a 4+ armour save. It's also an additional 4pts/model. This would make a 30-ork mob cost 300 points.
Nobs
While costing an additional 10 points before wargear upgrades, a Nob is as expensive as a Space Marine ... and he gets S4 and A3 in his stat-line. Considering Furious Charge, these guys hit like freight trains. Give them Power Klaws (+25 points) to really deliver the hurt.
Trukks!
Your friendly dedicated Transport Vehicles! It's a Fast vehicle, and extremely flimsy (Orks would have it no other way). At 35 points, they're very cheap. The only thing to keep in mind is the maximum capacity of 12 models. If you take a Trukk, you will lose the benefit of Mob Rule very quickly in exchange for possibly getting to the enemy faster. There is safety in numbers (and you can make this work for you both ways...).
Foot-slogging your Boyz will allow you to take advantage of 30-man mobs of Fearless T4 Orks. They're quite survivable, especially if you take 3 or more full mobs. On the other hand, Trukking your Boyz will mean each mob is less survivable, and in a very vulnerable vehicle to boot. To off-set this vulnerability, take 4 or more Trukk mobs. While one Trukk is very easy for your opponent to neutralize, 4 or more will make them sweat for sure.
Comparin' the Boyz to da Rest
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Gretchin
Ah, grots. They're only 3 pts/model, and have miserable stats. As with Boyz, you can have a mob of up to 30. Are they better than Boyz? Hell no. They suck in Close Combat, and their BS3 goes to waste on 12" guns, putting them in danger of being assaulted. So what are they good at? Meat-shields. If you're foot-slogging your Boyz, running a mob of Gretchin in front of them as a meat-shield is the best thing you can do with them. Your opponent doesn't really want to shoot at the Gretchin, he/she'll know that the real threat is your Boyz ... but if he doesn't shoot the Gretchin first, your Boyz will have a 4+ Cover Save. It's like taking the 'Ard Boyz upgrade, only for fewer points!!! It's a grot's life.
Nobz/MegaNobz/Biker Nobz
If you have included a Warboss as one of your HQ choices, you can have one Nobz, MegaNobz, or Biker Nobz unit count as a Troops Choice. This would put them in the same class as Boyz. Are they better than Boyz? Yeah. Pretty much anything the Boyz can do, these guys just do it better, and harder. They're extremely expensive, though ... so that one unit can't really invalidate the use of Boyz totally.
Deff Dread
If you have included a Big Mek as one of your HQ choices, you can have one Deff Dread count as a Troops choice. Deff Dreads can be geared for nearly any role, and if given a pair of Big Shootas, your one Troop-Deff-Dread could easily sit back while your Objective-capturing units hit the mid-field and Opponent's DZ Objectives... If you're considering having it be a close up unit, it may prove to be a bit more vulnerable than a good-sized mob of Boyz, with only a 12 AC on the Front and Sides. While vehicles have gotten a slight buff with 5th edition, it's still quite possible to take out with a single heavy hit. While the Dread can be taken as a Troops choice, the reason it really doesn't compete with a unit of Boyz is that as a vehicle it can't capture objectives.
