What are you guys using on your core, Legs, Arms, Head, Core, Back and Arm Weapons, and Boosters-Generator-Fcs, Ect...
Seraph 2
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2 laser cannons on the back
laser rifle
Moonlight Laserblade
2nd Core
Lightweight arms
Semi Heavy Weight Legs (6100 WP)
Best Boosters, Generator, and FCS

I use head:most expensive
core:the most heaviest
legs:the biggest 2 leg style costs 64000
Arms:most armoured and heaviest
Weaponsowerful laser weapon costs 75000
moonlight
laser cannon on the back along with the best radar
best FCS,generator,boosters

Sounds good, but whats the grade?

Here's what got me through most of Armored Core, the origonal, as soon as I got all the parts I needed.

HD-9066 (The humanoid one with the slit eyes)
XCH-01 (HEavilly armored core with the bubble back)
AN-K1 (Best arms, just ask 9ball!)
LN-501 ("Cowboy" legs because the feet look like boots)
GBG-10000(Best output, recovers better than the gold one)
TRYX-BOXER, or QUAD (Depending on mission, extends FCS size without sacrificing range)
B-001 Extremely lightweight yet has decent efficiency.

You might notice that there isn't much room for weaponry, but that can be tweaked in by switching out the AN-25, and the HCL-01 for more weight allowance. In that configuration, it'll carry the KARASAWA, and a light sword, or a lighter hand weapon with some missiles. I usually carry one of the energy rifles because they don't cost anything to fire. A cheap MG is good for anti-aircraft, my preferrance is the MG500.
Good ground speed, manuverability, and flight time, but with decent armor, and sheilding. I basicly picked parts for their ballance of stats, and weight. Making the changes above may net you more carrying capacity, but you'll lose survivability with the lower defenses.

FIrst used in the "Stop security MTs" mission, I could barely afford it by not taking any damage, and using only energy weapons so I didn't have any expenses. The best way to do this is to save after each mission, and redoing it untill you get it perfect. Some missions, mostly later, cannot be done perfectly.

HD-4004 (Cheap, light head with radar, all the way at the bottom.)
XCA00 (POS starting core, untill you can afford something better)
AW-XC5500 (The plasma cannon arms, extremely powerfull)
LB-4400 (Cheap reverse joint legs)
GBG-10000 (As always, first thing I buy)
B-001 (The internal parts dont change much)
TRYX-Boxer (The legnthway window is nice, if you can get it.

That's it, basicly the insanely powerfull plasma arms on reverse joint legs with the GBG-10000, and radar. In the mission it was designed for, you just zig-zag down the street, and push the fire button down long enough to put to shots into the target whenever you get a lock. THey have missiles, but that's what the legs are for. Just jump when one is comming, then straffe in the air to dodge them.
A couple words of warning, first, there's just enough shots to kill all the MTs with a couple if you miss. Seccondly, the arms drain a lot, so don't boost.
Later in the game, an upgraded version is great for the mission where you get the FCS optional part. Get the LBKS-2B45A legs that look like they're wearing sneakers, the "Bubble back" core, and a better head. This time, stay off the ground to avoid mines, and use pop-up attacks from the hills to destroy the tanks.

Like anyone who's been playing this a while, I've got lots of designs, and a few favourite parts. Generraly, when I have enough credits, I just buy all of these, and stay out of the shop unless I need something special. This allows me to retool for each mission rather painlessly.

Heads: My fave is the 9066 because it's light, but with good sheilding and armor. It also looks real cool. On the down side, it's also high drain, so I'll usually swith out for another if I'm worried about having enough energy.
Seccond place is a tie between the ONE, and RADAR. The former is low drain, and has a good range, but the latter is high drain with the best of any head in the game. Neither has decent sheilding, though.
Arms: As far as I'm concerned, thes serve as extra armor, and sheilding in adition to their weapon carrying capacity. I like them light, so it's always a toss up between the AN-25s, and the K1s. The first are the lightest in the game, and have a little more armor, while the latter are better sheilded. I usually go with the K1s unless I'm slimming down to stay under weight.
Weapon arms: Best used on quads, and tanks because they cannot use swords. My favourite is of course the plasma cannon which can melt damn near anything, including you if you get too close. I'll use the MG25/2s for VS, but it's not as fun in this version. The AW-30/3s are the lightest in the game, which is good for making a cannon toter with something on the shoulders.
Cores: Just going by the numbers, the HCL-01 "Bubble Back" is the best. I'll use the lighter one to cram in Options, but I'd really rather have the defense of the heavy one. The stock core is complete garbage.
Legs: First off, I like RJs. They're manuverable, low drain, and can jump phenominally well. On the down side, they have nearly no defensive value, so I usually use the heavy core (above) to compensate. All other stats, speed, capacity, and armor, are about the middle of the road. I like the LBKS-2B45A best because they're the fastest, and best sheilded.
Homopoid(LN...)- Basic bipeds, the 501s have the best stats. While there are faster ones, they're really not that much quicker, and don't carry nearly as much. For heavyweights, I go with the 3001C("Adidas" legs). Again, there are heavier ones, but these are more stable, and kneel quicker.
Arthropoids(LF...)- Fast, and stable, they can fire cannon on the go, and back up at full speed. I really don't see any reason not to go with the lightest, or the heaviest. They've got the best stats anyway. I will warn you that they can't use swords that well. Tte catipilliars(LC...) are pretty much the same, but slower, and without jump function. I hate them, and only use them when I want to save money on the booster.
Internal parts(Generators, FCS, and boosters) Rarely change, I use the GBG-10000 exclusively after the first mission because it recovers quickly, and has the most power. Boosters are always either the B-001, which are lightest, and the B-P351 which are the most efficient. FOr FCS, it really depends on weaponry, and mission. The TRYXs expand the window without shortening range, so it's usually one of those. I'll use the QX-9009 only if I'm carrying nothing but wide/shallow weapons, and I want more range.
I'll get back to you on weapons, because that promises to be a long post by it'self.

As promised, here's my thoughts on weapons. First of all, Rifles suck. If you came into the game with it, sell it in the store, and never get tit back because it's bound to be useless.
Machineguns are nice for hosing down weenies in that kind of mission. The best has to be the MG-500, because of it's ballence between firepower, and endurance. The wide/shallow window means it's easy to lock with, while the "Special" used by the AR1000(Among others) is essentually narrow, and shallow!
Handguns are most usefull against "Grasshopper" Mts, and light bipedal cores because they tend to be stunned by the impact. This allows you to string shots together, or come in for a slash with your sword. I like the yellow shotgun best because it's easiest to hit with. All of them have the Wide/Shallow window, and lack the range to make deepening it neccisary.
Sniper Rifles are reasonably usefull if you can pick your shots while moving. E-rifles are pretty much the same, but drain your charge, so you want a solid backup. Also, you can maximize energy with option parts. I usually use energy in missions so I don't have to spend credits on ammo
I think the best back weapons are the cannon. True, you can't fire them running, or in the air, but their variety and power more than make up for this. Besides, the quads Can fire them on the move, so make great gunships.
The best, hands down is the WC-01QL. It's light enough to tack onto most cores, yet has enough power to destroy anyone it'self. This is balanced by it's high drain, so it's actually good that you can't shoot it while boosting. It also "Splashes", so it ain't a close quarters weapon, and you don't want to use it with freindlies around.
The GN230 is nice, but heavy, and slow. Basically a feild peice, it's really best for demolition, or slow moving targets. I use it mostly for a backup when my charge is down. The CN35 chaingun is another good solid backup, and hoser, but not real accurate. The LN350 linear is better because it stuns, has a good fire rate, and is almost as light as the 01QL. Incidently, both of the latter have that damned "Special" window, so you'll have to compensate.
Slug guns are just plain useless. I can't hit a damned thing with them, the shots are slow enough to dodge easilly, and the reload time is unaacceptibly long for something so weak.

Basically my multi-ppurpose design, it does just about everything reasonably well, but none excellently.

HD-RADAR (Best range)
XHC-01 (Good Armor)
AN-K1 (Best Arms.)
LFH-X5X (5000 WPs!)
GBG-10000(Best Generator)
B-P351 (Efficient)
TRYX-QUAD(Solid gun)
WC-01QL (Plasmatic death)
WM-PS2 (Triple Missile)

A generalist can beat any specialist by not playing their game. This design has good speed, armor, firepower, and most of all versatility. It doesn't fly good, though, and is weak up close. The latter, though is a lure for those bladers, because I can back up almost as quickly as they can chase me, and get several rounds of MG into them. The Plazma cannon is great for sedentiary tanks that can't dodge, or handle the energy. The missile is primarilly anti-aircraft, with the MG pulling double duty. There's no sword, because I don't play REBEL, and the wave sword is in MOA.

There is no such thing as a perfectly balanced AC. Every AC is weak against another type, this includes "balanced" ACs. Most of the AC in this topic seemed designed for missions, and to fighter against CPU ACs. ACs meant for tournaments against human competition are designed a bit differently. Most of the ACs here are too slow. PsiBerzerker your design is the only one I would use if I entered a tournament, but that design is weak against a Blade Specialist.