This is not a guide, but builds for the five champions:
Malphite, Kennen, Gangplank, Nunu & Singed. It is not usual builds, but rather chaotic crafting. This is the story about one time, where Coon & Friends got badass drunk and bought uncommonc clothes and accessories.

Let me throw out a huge thank you to Chaotic Bliss for inspiring me to try more alternative ideas on champions and make a build about it. Check out his builds, they are really original and plain fun. This probably isn't as chaotic as his stuff, but it is definetely not traditional.

I really recommend that you use these builds in premades, since people often will rage, since you do something uncommon. I haven't searched forum threads, so I don't know if these ideas are original. But I felt like posting this, so don't go angry mode, if you have seen similar ideas before. x)

I hope you will enjoy it! xD

AP Tank Teemo

This build focus on making Teemo and AP tank, which makes him a disturbance in teamfights, where he is able to run around and place shroom under opponent's feet. This way he screws them over, and this is also the reason why CDR is so important. Furthermore it allows him to run to their AD carry and blind him/her, without being killed too fast. He is a bit like a normal Trundle, who is trying to create chaos in the enemy team. He is not that good a pusher compared to the rest of these champions, but he is beefy and cute. The deadliest combination known to man!
The summoner spells focus on mobility, which allows Teemo to create a better mayhem in teamfights with his mushrooms. Just make sure that you always have 3 shrooms ready before a fight.

Alternative items are:
Randuin's Omen - It ****s up the enemies in a teamfight even more, due to the active. Furthermore the HoG provides money each 10th second. Tankmo is not that good a farmer compared to when he goes for damage.
Rod of Ages - A tanky AP item. Can be good if you don't need THAT much survivability, but only a little. However, it is best to get early on, where it can be somewhat hard to decide between damage and survivability.
Sunfire Aegis - It will do some damage in teamfights, while you rund around and place shrooms and blind people. Furthermore it gives some nice tanking stats.
Banshee's Veil - Against heavy nukers like Annie.
Quicksilver Sash - Against tons of CC. You need mobility to be able to run around in teamfights, so having a free cleanse once in a while is great.

Hybrid/offtank Singed - With sick movement speed!

This Singed is super fast and he is a good pusher with PD & TriForce.. He has great chasing capabilities, due to his slow, his extreme movement speed and his slowing standard attacks. (TriForce)
Furthermore he has decent survivability. He has a good amount of CDR, which makes him a bigger threat in teamfights, where he can slow carries and fling them around, due to his awesome mobility. He can also crit for quite some damage, since he has Trinity Force & Phantom Dancer. You can also go with Lich Bane for more damage on Q, but since you have PD, TriForce works better.
The summoner spells are to get more speed for chasing and to finish off an enemy on low HP and to shut down champions as Vlad, Mundo & Swain.

Alternative items are:
Hextech Gunblade - Gives your spells more damage, while still giving you the AD needed in an AD build. It also has a nice active, which makes it even easier to chase.
Zeke's Harbinger - If you have 2+ AD champions on your team, this can be a nice addition.
Shurelya's Battlesong - Nice stats and a nice active. Mana regeneration is a nice feature on Singed. Furthermore it gives CDR, which makes you able to fling & ult more often.
Quicksilver Sash - Against a team with tons of CC.
Nashor's Tooth - CDR, AP and AS. Nice for a hybrid build.

AD/offtank Nunu

This fella has a nice steroid in his W, which increases AS and MS. His snowball is great for chasing, so getting AS and red buff is a nice combination. The bad part of this build is that, his ult scales really well on AP, but this guy is a great pusher, a nice farmer and an awesome chaser. He is rather tanky, while he can deal a nice amount of damage. His W also scales well with PD & Youmuu's. More AS means more free spells, but with the CDR from the items, starting off with a Tear of the Goddess is a good idea, to keep up your spamming.
The summoner spells are picked for better chasing/escaping and for removing CC while chasing. It will make you unstoppable xD

Alternative items are:
Aegis of the Legion - If you lack both MR and armor and you think your team needs the aura. 8 damage doesn't sound like anything, but if a whole team gets it, it does do a different.
Hextech Gunblade - Your spells scale so well on AP, so going a bit hybrid is not a bad idea. The active is awesome, since it allows you to slow two enemies in every fight, in order to create chaos in the enemy team. (AP & AD carry)
Last Whisper - If the enemy team stacks a lot of armor, this item will come in handy. It is not as expensive as other AD items, so if your farm is lacking a bit, it can also be a nice addition to your item build. However, it scales best with physical spells imo, so I have doubts about how well it works compared to other items.
Guardian Angel - If you need both MR and armor and you feel that it's passive can make a difference in fights. The enemy team will probably focus you when you ult, so letting them throw of tons of their CC and damage to stop it can be awesome, when you simply revive again.
Boots of Swiftness - These boots will make you the ultimate chaser and give you better roaming capabilities.

AD Kennen (with a bit of AP)

This fella will stun.. a lot. His ultimate won't do that much damage, but with the high movement speed from PD and TriForce enemies wont escape it. He will however, do tons of damage with normal attacks and stun often. He is a nice addition to teamfights, due to his massive CC and a great amount of damage from standard attacks. You also have the ability to push towers quite decently, which is something that all these five champions have in common with these builds.
The summoner spells is focused on chasing/escaping, complimenting your ult & to shut down an enemy. It will help you in laning phase as well as in teamfights.

Alternative items are:
Infinity Edge - Sick crit damage and a huge amount of damage. If you dominate like a boss, this is not a bad idea.
Bloodthirster - If you want laning sustainability, this item is awesome. Furthermore it allows you to push after a teamfight, even if you are low on HP, since you regain it fast. I recommend this in games, where you don't die a lot and/or games where you need to push.
Frozen Mallet - If you lack survivability, you can grab this instead of TriForce. However, you might feel that you lack damage in lategame, if you do so.
Guardian Angel - If you need both MR and armor and you feel that it's passive can make a difference in fights. The enemy team will probably focus you when you ult, so letting them throw of tons of their CC and damage to stop it can be awesome, when you simply revive again.
Wit's End - If the enemy team is stacking armor, then you can grab this to encounter it with magic damage. It makes you really strong in 1v1 against casters.

AD/Offtank Malphite

Malphite has a nice built in steroid when he uses his W. The CDR boots is to be able to use that steroid more often. This is a trinity tank version of Malphite, which makes him a great pusher - His W-ability gives a sick towerpushing element to AD Malphite, a great chaser with sick movement speed, a good initiater - his ult, and he is also a great farmer, due to his splash damage passive. However, this guy has low base AS, which is why runes are focused on buffing that. Philosopher's is to solve some mana issues you might have, since Seismic Shard is quite spammable. However, that item is sold to make room for more late-game efficient items. I've considered using Frozen Heart instead of something else, in order to get more CDR. Maybe instead of Banshee's since Warmogs is a nice defensive item against casters. I would have to test this further though. You should not play completely like a tank while using this item build for Malphite, since it lacks resistance. Play like an offtank, though you can initiate fights. Just be careful when it's teamfights, since they might focus you down.

Alternative items are:
Frozen Heart - Cooldown Reduction
Youmuu's Ghostblade - The active works awesomely well your steroid. However, you will lack some AS if you go with this instead of Phantom Dancer or something else.
Frozen Heart - If you lack survivability grab this instead of PD.
Berserker's Greaves - If you want more AS and don't feel the CDR is that necessary.
Hexdrinker - If the enemy team is mainly casters, so you need survivability against magic damage, while you still lack a bit of damage, this is a nice blend of both.
Aegis of the Legion - If you lack both MR and armor and you think your team needs the aura.

I know this guide/build is rather short, I might add to it, if people give me some nice ideas through constructive feedback. This is in no way a guide meant to get good ratings, since the item builds aren't traditional and not the best ways to play the items. They are simply another way to play them, which requires more practice and that you are willing to have some bad games, before you master the given playstyle for these weird item builds.

Hope you enjoyed reading and I hope you will try out one or more of these builds. It's really funny.