Maybe not the best but leveling up, Ive found more than a few purple synergy’s that can hold its own.
Jakobs unique pistol: Law
The 100% melee damage says even a low level (16) can be used efficiently for quite some time. It’s the elemental lack that keeps this one absent from a lot of peoples backpacks I guess
Can also be used to pretty good effect in conjunction with the unique shield ‘Order’. Which in it’s own right can be a very decent item especially if farmed for an element resistance.
Prior to dlc, the Law pistol was the best melee weapon in the game, I think it’s more that fact that people overlook it for, it isn’t the best anymore. But still a great weapon
and the melee stays the same 100% at any level, in theory you can use a level 16 Law at OP8 if you’re only using it as a melee weapon.
The CHOPPER.
Do I really need to say much ? I love this thing but it sucks :’(
I also really like the Chère-amie, Commerce and Nukem.
Though my favorite launcher is the Topneaa, I have a soft spot for the Nukem and Tunguska. Neither one of those is usually considered TG (esp the Tunguska) but I do enjoy using them regardless.
I love these too!
The babymaker was my all-time favorite weapon.
Practicable Face Time! (I sound like a broken record here) I’ve never seen anyone else use it on video or mention it, and the thing is a beast on Maya, or on Jack in TPS!
Also a fan of the Emperor. Took the time to farm corrosive and incendiary versions some time back, and still use them. Used the corrosive one in my most recent Maya video, in fact. The burst is so tight, it’s easy to stack crits at long ranges. Especially enjoy it with a Maliwan sight.
This. 
I use a Diamond Face Time on Zer0 with the Critical Hit accessory, it just melts through enemies very quickly. Hyperion Shotguns are so great, especially the Developement (the one with the Torgue Barrel).
The Lascaux (amazing what you can find in a puddle)
Tip top smg, suffering only from a lack of element. That said the fact it’s free and also possibly the easiest weapon of quality in the game to farm multiple times whilst hardly moving???
I think the closest you could get for easy farming x-amount of times is the Gwens head, as already mentioned by @Carlton_Slayer
I could be wrong there could be easier than these, but…
IMO the benefits of this weapon outweigh it’s significant but still only the one minus!
Farming both removes that problem too as Gwen’s Head comes in all elements 
Intrigued now as to how easy it would be to loadout a specific set of high-quality yet very quick & simple to aquire weapons…
For example I would not include say the Harold farm, easy as the farm is, Mr Lee can take his sweet time dropping one!
Tinder would also be out, as all drops are randomised.
Sorry, I’m starting to derail again… 
For me, any farm that requires minimal legwork counts, regardless of how likely the drop is. Knuckledragger (using the SS exit spawn point), Savage Lee (possibly two attempts per run if you get him spawning near the fast travel), Boll, McNally, Mobley, Gettle, Mick/Tector, all very easy to get to for farming.
Of course the Lascaux and Gwen’s Head are a little different because they don’t require fighting (although Lascaux will probably require some), so they are very simple.
My favorite weapon in the game is the Flakker. It gets a lot of flak (pun totally intended), but I love the damn thing. Once you figure out how to use it and get some practice, it’s a lot of fun. Also, I’d say that every single piece of Jakobs weaponry in the game is a favorite of mine, be it unique or otherwise.
I have read many things suggesting the Flakker is amazing, but i’ve never been able to get those results. Is there a guide somewhere that offers advice on using one?
Law & Order are also very simple, minimal travel and guaranteed.
And i know the likes of Mobley and Gettle etc, but those can and sometimes do turn into seriously long marathon farming sessions!
And anyone of us who plays this game more than others, as I’m pretty sure most of us here do
has been on the receiving end of at the very least one of those 
Simple, or only the slightest of fuss involved! Guaranteed to get is the thing, good to high quality armaments. Orphan Maker for another example, Rubi and so on…
Might have to take a run out 
I think @Derch may have done one of those
To be fair, pretty much everything is a beast in Jack’s hands. 
One of my favorites as well, but isn’t it one of the top weapons in the game? Seems to fail the “Even if they aren’t considered great” part of this thread. If people don’t consider it great (and they are wrong, because it is great!), then yes I totally agree with you! 
Once you get a feel for the range, you should be fine. I treat it primarily as a boss-fight weapon since it’s just devastating on enemies large enough for most/all pellets to hit. A level 13 world drop Flakker utterly trivialized Wilhelm, the Gluttonous Thresher, Badass Pyre Thresher, and several constructors for three of my characters, for example.
It is great. It is also one of the most hated weapons in the game and it probably has one of the steepest learning curves of all weapons.
Even if you do learn how to use it properly, it might still not be your cup of tea and the results will still be fairly inconsistent. It’s kind of an unreliable, slightly situational weapon, but when most of those explosions hit the target, boy, do they hit hard. The challenge is trying to hit most of those explosions every time. First thing you have to do is get the right parts. The vertical grip accessory helps a lot on this one (more explosions = more hits). Second, learn its effective range and try to keep that distance from your targets most of the time. This is very important. It will be useless in close range, against small targets and against enemies that rush towards you. However, it will excel against large targets and grouped up enemies. For these reasons, singularity grenades have great synergy with it. You can use them to group up enemies and keep them at the right distance. Third, aim a little lower and sometimes even shoot down on enemies with it. When using it, keep a second weapon ready for emergencies and think about how your build and the rest of your gear works with it. Other than that, it only takes practice. It is my primary weapon on Axton. I use an explosive damage relic and the Bee as a shield (Axton is great at keeping it up and the Flakker really gets a lot from it). My secondary weapon is an Explosive Fastball. With this setup, I can clear every map at OP0 using nothing but the Flakker and a few grenades.
Sounds like a challenge playthrough if ever i’ve heard one 
One of my favorites as well.
its (even if)
which meaning it doesnt HAVE to be considered not great 
and on that note weapons that I love are…
SWORDSPLOSION!!!(which is a great gun but still)
Tunguska
Flakker
Bandit Unique Shotguns(Teeth/Dog/Jolly Roger)