I haven't been able to afford many 3rd party toys, so my list is pretty small. I've steered clear of the stuff rom CrazyDevy because I don't agree with their piecemeal selling business model and I consider their stuff way overpriced for what it is. iGear have yet to do anything that impresses me; I liked the look of their Ark playset, but the awful fit of the parts puts me off.
Anyways, here is what I have:
Shadow Commander (KO)- Got because I loved the design but couldn't afford the genuine article. I even bought an SDCC Nemesis Prime specially for it cheap at Botcon last year. For a KO, the quality is excellent; some parts are a little loose fitting, but that was dead easy to sort out.
Headrobots Crystal Cobra (MegaToyFan exclusive) - I'm fascinated by designs that we never got, and this was inspired by a cancelled Headmaster design so it was too good an opportunity to pass up, so I asked HiQ to pick me one up from Megamus at Botcon this year. He's a beautiful figure; even the packaging is lovely. He's going to go on a Highbrow junker I have.
Justitoys' MP-05 Masterpiece Megatron upgrade set - This was an absolute no-brainer. I love the MP Megs design and the chance to "complete" him was WAY too tempting. He looks INSANE with the stock & barrel fitted, and absolutely massive. Also, the die cast handle pieces add a lot of stability to the robot mode (as well as a fair bit of heft to the gun mode).
FP Munitioner & Explorer - I'm a massive G1 Bruticus fan (he was the only combiner I had complete as a kid). I have my original loose G1, a sealed G1 Classic Euro release, Car Robots Valdigus giftset, RID Ruination, and Urban Camo Ruination. I HAD to get this to go with them. I wanted this upgrade as soon as I saw the photos, but I didn't have the money at the time. Fortunately anabolik1 on these very boards hooked me up with them both MISB, as well as the 3 ROTF figures needed to go with them.
Justitoys' WST Dinorobots Grimlock, Swoop, Snarl, Slag & Sludge - First time I saw a pic of "Snarl" before he came out, I was amazed by how G1 toy accurate they were. Other than the sticker sheets being terrible, I can't really fault any of them. I also have the limited version of Snarl in his original toy colours (not the gold chrome version, unfortunately).
Justitoys' WST Shockwave - I LOVE the G1 Shockwave toy; along with G1 Megatron & Trypticon, he's probably my favourite toy. Nuff said. Plus, he comes with a custom fist for G1 Bruticus to hold him in. Genius.
Justitoys' WST Blaster - yeah, I'm a Justitoys fan. With the exception of the awful sticker sheets for their WST Dinos, I can't pick faults in anything they have done that I own.

I'd like to pick up Protector for my Classics Rodimus, and I do want to get Defender at some point. I'd love to get the FP Superion upgrade, but it's way too pricy for me to even consider right now. Maybe in the future.

 

1. Faith Leader : Just to make Optimus 'in-scale' with the other MPs, and Igear will definitely make mini MP Megatron.

2. WST Ultra Magnus Perfect Model : Because there's no Perfect Model in original WST.

3. PO'd FP Protector : Because I love Classics Rodimus, and he deserve that 'Prime mode' add on.

 

1.FansProject City Commander
( No official Classics Ultra Magnus armor/trailer.)

2.FansProject Warbot
( No official Classics Triple Changer Springer and after the hideousness of Classics Astrotrain & Universe Octane I wouldn't trust Hasbro to do a decent job even if they made one. )

3.Perfect Effect Rumble & Frenzy
( I didn't want the G1 reissues and have no intrest in the Hasbro tank versions. )

4.iGear Faith Leader
( I wanted a proper G1 style Prime to lead my Classics Autobots in place of the mediocre Henkei Prime. )

5.WST Dinobots
( No official G1 reissues are happening so these are a suitable alternative. )

I like supporting the 3rd party companies because they make stuff I'm intrested in and from a design standpoint it's often superior to the official stuff.

 

Currently I've got:

1. FansProject City Commander
The original release, HAD to get this to make my Magnus look complete. Finally justified getting that thing from awhile back. Unfortunately being the initial release it lacked the shoulder launchers and transforming rifle.

2. ALT/BT Chrome Shoulder Launchers
Really complemented the look of all my Alts, particularly the Smokescreen and Jazz figures. Took forever to track them all down on eBay but was well worth it.

3. G3 Trailer
Provided Prime his iconic trailer and came with a pack of weapons for my Classics figures. Enjoyed it very much and its a great display piece with some posed figures.

On the way:
1. Protector
Just preordered this along with the rest of the stuff below from RobotKingdom. Will give me something to look forward going home to post exams. My Rodimus really wants his upgrades =)

2. TFX-03
The launcher and gun set for FP City Commander to complete the sucker.

3. Sidearm
To complete Protector

4. Warbot
Couldn't get him at TFcon so I waited till now to put my order in.

 

1) FansProject Warbot Defender aka Springer - Wanted a proper Springer.

2) FansProject Munitioner & Explorer - Love how the upgrade set looked.

3) Just ordered Perfect Effect Frenzy Rumble to go with my music label Soundwave.. I think these are in perfect scale and look great!

 

Justitoys WST Blaster, Shockwave, and Dinobots
Hereostoys WST seekers
It's awesome to have smaller figures in their alt-modes in front of their larger counterparts.
Forgot who made it but the transforming Masterpiece Roller for MP04 Prime.

Reprolabels for G1 Thrust, Ramjet, WST Constructicons

 

City/Shadow Commanders and the Animated Accessory kit.

Because I wanted them.