Now, you can't talk about Regigigas without highlighting it's biggest problem, Slow Start. Regigigas is the ONLY legendary to have an ability that straight up hinders it. It's almost like someone in game production hates him. Slow Start halves Attack and Speed for 5 turns. Anyone who plays Double or Triple battles knows lasting that many turns, especially without recovery moves, is extremely difficult to say the least. Oh, did I not mention that Regigigas practically has no recovery? Well it doesn't, outside of Drain Punch. Normal typing is rough too, seeing as Fighting moves are so common.
Not everything is terrible for Regigigas though, it's just hard to cut through all of the bad. First off, Regigigas has a great movepool like most Normal types. Real standouts include the elemental punches, Power Up Punch, Drain Punch, Return, Payback, and Knock Off. It even has some moves that can help it outlast Slow Start like Double Team and Substitute. It's stats are nothing to scoff at either. The only stat that is below a base 100 is Sp. Attack, and even then it's an 80 which isn't too shabby. Stat-wise, Regigigas is solid.
So, Slow Start? What do we do about it. Well, there are a couple strategies. For singles, run it alongside Cofagrigus. Have Cofagrigus with Red Card come out vs an offensive pokémon. If the pokémon hits Cofagrigus its Mummy ability will take effect and replace the opponent's ability. Red Card will then allow you to swap for Gigas. Next, have Regigigas hit the opponent, now Gigas has Mummy instead of Slow Start. It's stats will be back to normal immediately plus any other offensive pokémon that make direct contact with it will lose their ability which is pretty handy. This is sort of a one trick pony, but it may leave your opponent surprised as Regigigas starts wailing away on their pokémon.
When it comes to choosing moves for Regigigas, it really depends on what you what the behemoth to be doing for your team. If you want to try and outlast Slow Start, then stalling moves like Thunder Wave, Substitute, or Double Team are the way to go. I would suggest a more proactive approach, however, using some of the strategies from above. Anyway, the real gems of Gigas moveset were mentioned above, however I will outline some I would strongly consider:
- Return: This is Regigigas's strongest attack that doesn't have some sort of ill-effect or unpredictability. With the same type attack bonus (STAB) it is 153 power. You'll have to make sure Gigas's likes you, but raising it usually covers this.
- Fire/Ice/Thunder Punch: Worth mentioning for covering weaknesses of other team members. Just pick the one(s) you need.
- Power Up Punch: Regigigas with an attack nature and max attack has an attack stat of 460. However, if you decide to go with a defensive or speed nature, this could be used to make up for the lower attack stat. One or two hits from Power Up Punch, and you're golden.
- Drain Punch: It is Regigigas' ONLY recovery move. Without it, you are accepting that you will never heal the guy (unless you have a partner with Pain Split or Heal Pulse).
- Payback: Even at 100 base speed, Regigigas is still slower than a lot of common threats. Payback monopolizes on the fact it would be slower by doubling from 50 power to 100 after it is inevitably hit. You still need to dump Slow Start for maximum effect though.
- Knock Off: ALWAYS a good choice. Unless you're facing a Mega, you can ensure that your opponent loses that all to important item for their strategy. Knocking off an item also increases the power of the move. Always nice.
- Thunder: Wait... a special move? Really? Yes really. 80 base Sp. Attack is nothing the scoff at. Also, Slow Start has no affect on Sp. Attack, so Thunder is as good as it could possibly be, Slow Start or not. Seeing as most people who use Gigas would have it on a Doubles or Triples team, run it in the rain. Wynaut?
Knowing this, there are 3 potential movesets I plan on trying out on Gigas personally. There is the walling set, a physically offensive set, and a rain dance variant.
You Fought the Wall..
Nature: Impish or Careful
Attacks: Thunder Wave, Confuse Ray, Substitute, Drain Punch
Strategy: Again, I don't care to wait for Slow Start to end, so this would likely be combo'd with one of the ability stripping strategies above. Mega Lopunny works best, but this could be done with the Cofagrigus strategy in Singles too. Although you would think a strong attack stat wouldn't matter for a wall, it does for Gigas. You want Drain Punch to be as strong as possible for maximum healing. Anyway, set up status and stall as long as possible.
And the Wall Won
Item: Normal Gem
Item: Normal Gem
Attacks: Return, Knock Off, Fire/Ice/Thunder Punch, Earthquake
Strategy: I honestly just went through and chose Gigas's strongest most reliable moves. The set works best combo'd with Hawlucha giving Gigas Unburden. That way you get the speed boost, lose Slow Start, and have a max power gemmed Return all in one turn. That'll make your opponent shake a little.
Nature: Bold, Calm, Modest
Attacks: Thunder, Icy Wind, Thunder Wave/Confuse Ray, Wide Guard
Strategy: A weird set to say the least, and definitely in need of testing, this is a support Gigas for a rain team. Thunder has 100% accuracy so it's a no brainer. Icy Wind will reduce the speed of both opponents, and Thunder Wave/Confuse Ray are there for disrupting status. Regigigas can't get Protect, but Wide Guard is useful in Doubles and Triples. It potentially protects Gigas for a turn from range moves. It also means that Gigas's partner can use Surf without hitting Gigas.
So there you have it. Regigigas may never be game breaking, but it can be fun. The best way to know is to experiment with it and see what you can do with it. If anyone has any suggestions or battle videos showing their Gigas in action, feel free to comment below!