This is another good review of TIM from 2013, starts with some basics for the beginner 
LINK

I've recently switched to Noctua's NT-H1 compound and really quite like it. You need such a small amount, pretty much half the diameter of a motherboard capacitor's worth and you're good to go. I've never tried any of the electrically conductive ones personally but I don't think I ever would. While I like to OC, I've always left mine a bit modest and not pushing as far as it could go.

Better: GC-Extreme Thermal Compound

Best: Grizzly Kyronaut 
 
 

Applied indigo extreme exactly as intended. Threw it out when I spotted drips of it on the mobo. Half of it didn't melt. 5820k heat-output broke the seal. Too much gamble for my taste.
 
I don't really care which TIM is "the best". If it's popular and recommended I'll take it. Usually Arctic Silver 5 comes bundled with a CPU when I buy parts.

Lately i've just been using AS5 because I have been lazy with my applications, I didn't feel like waiting and it's all they had at Microcenter. My absolute favorite thermal paste was OCZ Freeze, but they producing it a while back. MX-4 was a great replacement for it though.
 
The absolute best thermal paste i've ever used was coollabratory liquid ultra, my temps were amazing. Spreading it took a lot of effort and cleaning it off to prep it for selling was not a simple matter either. I have considered getting their new liquid copper.
 
My next purchase will be Scythe Thermal Elixer 2, it looks like a good one.

 Arctic Silver 5 Atn90-3.5G is best cpu thermal paste. It is designed for modern processor and cooling systems. I have used this product last time. I am really happy with this product.

Heck, I still use Arctic Silver 5! works just as well as anything else and eazy to install blocks with without the BS.

I use Gelid extreme. 3 years later it still performs just as well compared to the first day I applied it.

 
Toothpaste ftw.
 

Gelid extreme, mx4 and less often last time - stg2(quality fell). These are hard to apply evenly, if used to smear all over the crystal/cover, and despite the fact that inexpensive they provide high-quality results.

At this moment in time if you go for any good brand you'll get same results every time. For last umm 5 years or so using same mix of TIMs - GelidExtreme, EK-Ekotherm. That's it. Whichever is closest to my hand I get it and don't really overthink the issue.
 
Gone are the days when most TIMs was conductive kind of paste and you had to really pay attention. Now TIM market is much more simplified and it really is just user preference. Of course excluding here extreme TIMs like some liquid metal plates or something. That's just vast overkill with nil performance gain in real life.
 

quadlatte

ypsylon
At this moment in time if you go for any good brand you'll get same results every time. For last umm 5 years or so using same mix of TIMs - GelidExtreme, EK-Ekotherm. That's it. Whichever is closest to my hand I get it and don't really overthink the issue.
 
Gone are the days when most TIMs was conductive kind of paste and you had to really pay attention. Now TIM market is much more simplified and it really is just user preference. Of course excluding here extreme TIMs like some liquid metal plates or something. That's just vast overkill with nil performance gain in real life.
 

not nil at all. i Use CL ultra on both my cpu and gpu, works great, my gpu max temps dropped 17c alone (on the stock air cooler with 60% fan set static for testing ) over using gelid extreme and cpu package temps dropped about 7c, once my dr delid tool gets here im sure those temps will drop much more. 
right now my gpu is at 27c with a ambient temp of 25, fan at 1400rpm, thats a drop of 7c from gelid paste. the best part is i can keep my fans low with less noise and still maintain good temps, well worth it in my book. 

Look I don't debate de-lided CPUs. I'm normal user which will never go into such extremities. I don't care about extreme OC one iota. For normal applications any good-brand TIM will do. Furthermore I don't do air-cooling on my rigs for a long time. It's highly inefficient and when you do liquid cooling TIM is just that. TIM with very much marginal importance as long as you don't go into some no-name cheap-o paste. Picking right waterblock is much more important than investing into some over-hyped TIM as coolant temp will equalize after couple hours rendering whole super-TIM investment null and void in no time at all.
 
Superb thermalpads for VRM that's entirely another story - well worth investment. TIM not so much. 

I like IC Diamond myself

I have used Artic Silver 5 for years. Stuff has been around for over a decade and still being recommended so I have a lot of trust in it.

Hoggle
I have used Artic Silver 5 for years. Stuff has been around for over a decade and still being recommended so I have a lot of trust in it.

It was great too because radioshack stocked it, so in a pinch you could go to store and pick it up.