XV104 Riptide Battlesuit
The XV-104 Riptide is basically what would happen if the Tau found a old DVD of Gundam, and got a hard-on. A battlesuit 'equivalent' (Read: Mainly Inferior) to the Imperial Knight, it is the Tau's largest battlesuit. Well, unless you count the two larger suits, but those are technically Ballistic Suits, and are a different classification of mecha. Resembling the lovechild of a XV8 Crisis Suit and the ZZ Gundam (from the Mobile Suit Gundam series of the same name), this mecha was once PURE AWSOME!!! Sadly (as of 8th Edition), the Riptide (Holy Mecha Emperor and King of The Warhammer Battlefield in 7e) is now crap. For reasons to be explained further on in this article, the Riptide is now one of the many units that the Tau once prided themselves on that is now rotting in a slum somewhere. Though (like the people at GeeDubs often say in previous codexes (and on the Riptide's webstore page)) it DOES make a great addition to your army. At least in the way of appearance. I mean fuck. It's a motherfucking gundam in 40k. I guess that you get functionality deductions for style, eh??
Fluff and that kinda thing
The XV104 Riptide was first introduced during the third sphere expansion of the Tau empire. When the Tau needed to break the siege at a pair of hive cities that the Tau were finding hard to use a cheatcode on. When everyone's favourite waifu Shadowsun was told of the failure to break through, she decided to break out the new toys that she had been saving up for her next 'relaxation session' with a certain Custodian. As a result of this order, so came the introduction of the ZZ Gund...sorry, the XV104 Riptide Battlesuit.
Striding onto the battlefield, undeterred by the shitload of dakka that was coming their way, the new battlesuits basically ripped the imperial defenders a new one. When the imperial troops sent guided missiles their way, the riptides were unscathed, protected by invulnerability chea...I mean Riptide Shield Generators. They stepped through existing holes in the walls....waait a minute. I though hive cities were collosal structures, hundreds of stories tall. You build a WALL around a massive CITY??? God, someone was reading too much news relics from the 3rd millennium. Anyway, if the Riptides were not stepping through existing holes, they were creating them with their High Mega Canno....sorry, Ion Accelerators. Jeez, too much power. I wonder where it all went???
Anyway, the RIptide soon spread through the Tau empire, being the lure for thoudsands of preteen GW customers with too much money and not enough playtime. It soon reigned supreme over the fluff battlefield and the meta one. The reason in the fluff for the pathetic real world cost of around $130 Australian Dollars is that the Riptide's extremely tough and 'impenetrable' armour is made from a super-rare material called Fio'tak. The real-life reason for the cost is that GeeDubs are pathetically just screwing with you to get your money. Lucky you're not paying for a resin model, huh?? They use a super-powerful engine called the Nova Reactor to overdrive their capabilities to the max, allowing them several things on the tabletop, most notable the ability to overpower their two weapons. Sadly, that leads to the tabletop issues in 8e:
On the Tabletop
As of 8th Edition, GeeDubs decided that they couldn't have the riptide spam of 7e. So, as with all good things, it came to a end when they decided to make the Riptide take a mortal wound every time it uses it's Nova Reactor. But this is exactly what was in 7e, you may cry. The Riptide took wounds even then!!!
Well, my innocent children, that is not exactly true. Yes, there was a chance that it would take damage, but only a 1/3 one. Now, it takes a mortal wound every time. The only way to avoid it is taking the Stimulant Injector upgrade, which gives Feel No Pain. This allows you a 1/6 chance to avoid losing damage, which is substantially less than what it was in 7e, and also costs a few extra points, which would be otherwise better spent on another of what should be two upgrade hardpoints.
In addition, the Heavy Burst Cannon (the standard upgrade) is weak as hell. It gives a increase of one strength unit from the standard Burst Cannon found on XV8 crisis units, and other than that, just more shots. The ion accelerator (which is arguably the better weapons choice) costs 104 points on top of the already expensive unit. This means that you'll maily be using your huge-ass suit in a anti-infantry role, and not actually blowing holes in enemy Imperial Knights. In fact, this relegation to a inferior and already-redundant role means you'd be better off spending the absurd amount of money on a unit like the Hammerhead Gunship, which can put some dents on a enemy titan for a cheaper price.
In summary
Basically, buy if you want, but don't expect to get much milage out of the suit. If you already have a few left from 7e, and you want to put them in your list again: you better not. It will cause too much tears on your behalf. In fact, you'll be sobbing about not playing adeptus mech and getting those sweet imperial knights from Forge World.