Dark Souls

NOTE: I have had people comment saying the dashboard trick to save your Titanite Slab doesn't work. The game has been heavily patched since release, so there is a chance it won't. If you take a chance with the trick, it is at your own discretion, so be careful and make sure your dashboard as soon as the achievement pops.

The dashboard trick still works as of 30th December, 2023

Also, as another user has mentioned in the comments, you can simply get a friend to drop you the weapon when they are in your game and the achievement unlocks, so if you have awesome friends then it cuts out a lot of the work. The same can probably be said for the rest of the weapon achievements as well.

When you get to Sen's Fortress, there will be a room you HAVE to go through after chasing boulders down 2 sets of stairs. This is where you meet your first mimic (a monster disguised as a treasure chest) and upon its defeat, you are rewarded with a lightning spear. At this stage in the game, it's the only Lightning Weapon that you can find. All you need to do to gain this achievement after is to upgrade it to a Lightning Spear + 5 and 'POP' achievement is yours!

To upgrade this to a + 5 you will need :
Lightning Spear +1 = 1 Titanite Chunk
Lightning Spear +2 = 1 Titanite Chunk
Lightning Spear +3 = 2 Titanite Chunk
Lightning Spear +4 = 3 Titanite Chunk
Lightning Spear +5 = 1 Titanite Slab

You can upgrade this to a +5 yourself at a bonfire (if you have the smithing boxes purchased) or any Blacksmith

The weapon itself (currently using) is pretty dam good, does decent damage and like most spears you can hold your shield up to block AND attack at the same time! Very easy-to-use weapon for novice souls players, or those wanting a slightly easier time.

For obtaining the items needed to upgrade the weapon, here's what I found:

-- In the Great Hollow there are at LEAST 2 chunks found while descending the Tree, I can't name specifically where but I found 2 along with other coloured chunks.

-- The Royal Sentinals, the two big guys in Anor Londo in the hall right before the boss fight, drop chunks (you'll know which ones they are because they can also use Healing Miracles) I personally farmed these for an hour and only got 1 chunk, the best bet is the bonfire outside of where you obtain the Lordvessel (the massive women) and run down the elevator, run through the room you fought the dual bosses and kill the first knight, then run back to the bonfire to reset them. The reason was it took too long to kill the other one while the Black Knight on the stairs shot arrows at me, so it was faster to kill one and run back, but it's up to you.

-- The Darkwraiths in Lower New Londo drop chunks as well, though very rarely. These enemies can also drop the Titanite Slabs, which is rarer still. You best use backstabs to finish them off quickly if you choose this method.

-- So far as much as I can gather there is ONE definite Titanite Slab drop per game, its when you revisit Undead Asylum the second time (it's optional) from the Boss which is underground in the room you fought the original Boss at the beginning of the game. (walk on the floor and it will drop down into the new Boss chamber)

It would also be wise to note, unless you are going to be personally using the weapon for something, gather all the necessary materials required to upgrade and do it IN ONE GO. Once you do, and the achievement pops, DASHBOARD IT! Reload the save and you will still have the Titanite Slab which is the hardest to obtain.
(My friend and I have confirmed this works, though he used a Blue Titanite Slab)

Of course, you can get better Lightning Weapons if you upgraded them from scratch, but hey who wants to waste resources on that?

NOTE:This is a work in progress as I am not able to confirm everything as of yet

To create a Lightning Weapon you need to begin with a standard weapon ( one that you can appply pine resin to otherwise it is unique and will not work )

No Ember Stones beyond the lesser levels are Required for Lightning Specifically only the Giant Blacksmith in Anor Londo (which is after Sens Fortress)

Visit the blacksmith and to complete the Lightning weapon you will ultimately require 9 Titanite shards , 9 Large Titanite shards , 8 Chunks of Titanite and 1 Titanite Slab

Titanite Chunk - 100% drop rate off the first and third Black Knight in Kiln of the First Flame. These enemies do respawn

Titanite Slab - is a VERY rare drop off Darkwraiths in
New Londo Ruins and also a 100% drop off of the Stray demon in the Undead Asylum (tutorial area) underneath the place you fought the Asylum Demon (first boss about 2 min into the game). The asylum can be revisited via the massive crow who you can see at Firelink Shrine who brought there in the beginning of the game.

Here is a Chart which I believe someone named Oyabunn created so credit to him,One thing to note is that I believe Pure "whatever" is actually Slabs in certain versions though I may be incorrect.[URL=http://imageshack.us/photo/my-images/819/dksweaponupgrades31...[IMG][/IMG][/URL]

If you are looking to gather materials for every weapon upgrade achievement you will need a combined total of 90 Titanite Shards , 20 Large Titanite Shards , 24 Chunks of Titanite , 3 Titanite Slabs , 60 Large Green Titanite Shards , 16 Chunks of Blue Titanite , 2 Blue Titanite Slabs , 16 Chunks of Red Titanite , 2 Red Titanite Slabs , 16 Chunks of White Titanite and 2 White Titanite Slabs

TRICK-unverified, to get the achievement without using your items simply fully upgrade the item in one shot and wait until the achievement pops WITHOUT leaving the upgrade window thus not allowing the game to save the data then simply turn off the game and turn back on. Supposedly worked on Demons Souls

you can get a lightning spear, in Sins Fortress. you go to the area where you first see the giant boulders that hit the snakeman. head up there go thru the fog door. keep going till you get to the doorway where the boulders, are heading down and follow it down. go to the left and there is a room with a chest. this is a mimic. kill the mimic and you are rewarded with the lightening spear. level it up to +5 and it is yours.
To upgrade this to a + 5 you will need :
Lightning Spear + 1 = 1 Titanite Chunk
Lightning Spear + 2 = 1 Titanite Chunk
Lightning Spear + 3 = 2 Titanite Chunk
Lightning Spear + 4 = 3 Titanite Chunk
Lightning Spear + 5 = 1 Titanite Slab