The Psychiatric Ward

If you like free experience and nice weapons as much as I do, you'll love these.

-Chapter 4: Squawking Sticks have a 5% chance of dropping a very nice weapon for Lucas called the Good Stick. The problem is that this enemy is very annoying because it can summon others by 'chirping'. However, it's totally worth it, because if you get that weapon then, you won't need to get a new weapon for a while.

The Good Stick adds 27 to your Offense.

-Chapter 5: You can get yourself a Friend's Yo-yo if you manage to beat Li'l Miss Marshmallow. Don't underestimate Miss Marshmallow, though;she can be tough to beat if you're caught unprepared. Hopefully, you'll have Saltwater Guns with you, because those really help a lot.

The Friend's Yo-yo will add 20 to your Offense.

-You can also get some Mystical Shoes for everyone's favorite handicapped thief. However, these are ONLY available if in Chapter 5, and even then, it must be BEFORE you go into the clay factory! To get this very valuable weapon, you have to return to Tazmily and go back into Osohe Castle, where you had fought Mr. Passion back in Chapter 2. Instead of Mr. Passion, Lord Passion will be there, and he is kind of hard. Like before, throw a Smoke Bomb at the ghostly composer. That will help a bit. The best part about getting the Mystical Shoes is that you don't have to get any other weapon from the handicapped thief afterward.

The Mystical Shoes will add 40 to your Offense, and will boost your other stats as well.

This is NOT a weapon, but this item will be SO useful that it isn't even funny.
That's right, I'm talking about the Shield Snatcher, equivalent to the Shield Killer back in Earthbound. All you have to do is find seven pink mice children in a vast highway.

Mouse Child number 1: All the way southwest.
Mouse Child number 2: Right where you fought the Fierce Pork Trooper.
Mouse Child number 3: Outside the clay factory.
Mouse Child number 4: Right by the Energy Station. You know, next to the sign that says not to put signs near the ocean.
Mouse Child number 5: Smack dab on the middle of the bridge.
Mouse Child number 6: Tunnel, East of that seedy cafe.
Mouse Child number 7: You know where you found the sixth mouse? Go into the cave south of there.

After having found the children, return to their mother, and she will give you a kiss, and more importantly, the Shield Snatcher. This is an item you want to give to Boney, seeing as he's the fastest of the group. It may not be so handy right now, but in Chapters 7 and 8, you'll be glad you got this very important item.

Naturally, you don't get any during Chapter 6.

-Chapter 7: Welcome to the 1/128 items that are famed in this series! These weapons are WORTH IT, all the way, so don't give up on finding them until you've got them!

Lucas' 'ultimate weapon' would have to be the Mystical Stick, which is available once you encounter some Heftyheads. Heftyheads only have a 3% chance of dropping this item, but from my experiences, it doesn't take long to get the rare weapon. Wait until you get to the END of Argilla Pass and into Ionia's house before you go and fight them repeatedly, trying to get the Mystical Stick first, though. This way, you have a nice, nearby spot to rest at after you start running out of HP and/or PP. You can find these strange purple enemies near the end of the tunnel, too, so this is an ideal place to get looking.
Here's a tip: The Heftyhead is pretty weak to Ice, so use your strongest level of PK Freeze, which should be Gamma or Omega by now.

The Mystical Stick will add 90 to your Offense, and will boost your other stats, too. As a side note, once you get this weapon, there's no real need to get a new weapon for Lucas.

And now for our offensive PSI specialist, Kumatora! Her ultimate weapon of sorts are the Mystical Gloves, which are dropped by Monkalruses on rare occasion(remember that this is a 1/128 item.) This has always been the hardest ultimate weapon for me to get, but that's just me, I suppose. The Monkalrus are indeed those weird walrus-orangutan things that inhabit Tanetane Island. As silly as they look, don't underestimate these enemies, as they're really pretty powerful. They also have fleas, so hope that Kumatora or Lucas don't get them. The Monkalrus is weak to Fire, so us your strongest PK Fire, which I would think is Gamma at this point of the game, unless you went overboard with grinding and somehow have Omega. Be very careful, as usually, Tanetane's hot spring isn't very close to where the Monkalruses are.

The Mystical Gloves add 55 to your Offense, but more importantly, give you a boost in IQ, as well as other stats.

~Chapter 8: Naturally, the final Chapter has some pretty good equipment.
While this isn't technically a weapon, Hippo Launchers rarely drop Thud Charms(again, 1/128 item.) The Hippos on land have less HP than the ones in water, so keep that in mind. Both Hippo Launchers, however, are easy to put to sleep and have a weakness to PK Thunder, so use your strongest PK Thunder available, which is typically Gamma unless you went crazy with grinding. Then you would have Omega, most likely.

The Thud Charm adds 30 to your Defense, and from what I've heard, will give you something of a resistance to status problems.

Next up is the Goddess Ribbon. This is yet another 1/128 item, and again, it's not technically a weapon. However, this accessory is unique in that both Kumatora AND Boney( or whatever you named them) can equip them. While I highly doubt you'd want to get this item twice, I recommend going for at least ONE. The enemy that drops them is called the Love Walker, which is weak to Fire, so toss some PK Fire it's way, and definitely use your strongest version. This is typically Gamma or Omega.

The Goddess Ribbon adds 32 to your Defense.

And for Duster is the Horus Bandanna(1/128 item). The thing is to keep defeating Upgraded Robots, which, surprisingly, aren't very tough enemies from my experiences. Use PK Thunder constantly and you should be fine, especially if you use Gamma or Omega.

The Horus Bandanna adds 35 to your Defense, which is a nice little boost.

Did you say, "Awesome Cloak"!? I certainly hope you did, because that's what's next. The Awesome Cloak is a 1/128 item that usually proves to be useful to it's wearer, Lucas(or whatever you named the kid). It is dropped by Pigmask Colonels, which have the most awesome cape and are weak to Freeze. Use Omega because you should really have it by that point in the game. They have a shield when the battle starts, and they also use a PSI Shield, so be careful with that.

The Awesome Cloak is an awesome cloak that adds 23 to your Defense and gives you resistances to Fire and Ice.

Happy EarthBounding,
~S_M_D