All time favourite processor. That has to be any of the Vishera based AMD FX 8 cores.
I loved Vishera for its infamy. It received a lot of hate. A lot of it undeserved, simply because its reputation was already tarnished thanks to its older brother Zambezi. I found its price to performance to be fantastic. I managed to get into the FX platform fairly cheaply as I already had a 990FX board available from a previous build so my entry into AM3+ was just a CPU. Stock like all FX's it was terrible. But once you figured out how to overclock it, man it was amazing. A good core clock combined with a good memory and CPU-NB overclock really turned that chip into something good. 800+ CBR15 was pretty dang good back in the day. It was always such a pleasure when people asked about GHOST at LAN's and events and how their eyebrows raised when they heard what processor was running. It was a guilty pleasure of mine seeing their reaction.
And its also the processor that is responsible for my journey into water cooling and also case modding. I bought a nice Thermaltake Water 2.0 Pro specifically for this CPU, because the Hyper 212 I scavenged from GHOST's predecessor was just inadequate. But that Water 2.0 had a dead pump on arrival. So I just went bugger it. Just go full custom. And I went down the rabbit hole from there. I then started to think of more elaborate ways to push the overclocks. More and more elaborate ways to to prevent my midish-range M5A99FX motherboard from turning into a molten pool of slag once the overclocks went beyond what a 6phase board at the time should of been capable of doing. 4.8, 4.9, 4.95, eventually I got to 5.1GHz on my FX in its last few months with a delid and direct die cooling with liquid metal as my TIM. That CPU lasted for so long. 2013 until 2020. What a bargain in my opinion. I would actually STILL be running it now to this day if I hadnt of broken off (not bent) some pins after I dropped it during some loop maintenance. Since I was getting such good life out of it I had planned to keep that system going until the dawn of DDR5. It had no issues pushing a pair of R9-Fury X's in crossfire. So when the life support for Multi-GPU was finally pulled and I switched to my now V64 it had no issues pushing that either. And to be honest I miss that CPU. I find my Ryzen boring by comparison. I don't get the same thrill and excitement trying to push a few MHz above what Precision boost can do. What a thrill it was getting 25-30% more performance out of a CPU. Now with my Ryzen the best I can pump out of it is MAYBE 5%. I used to run 4.95GHz 1.48V with 2700CPU-NB on 2000Mhz DRAM at 9-10-9-27 1T. I delidded the processor got I used set of MFR based Corsair Dom Plat 2666's and pushed 5.1 at a little over 2133 cas 9 on 4 sticks of ram. The IMC only ever managed 2400 on 2 sticks. But that was still plenty fast back then. 50ms latency makes my Ryzen seem slow. Best I have managed on these C-dies with 1800fclk/3600 is 70ns.
Then the my next favorite processor is what started my overclocking journey in the first place. Much like the FX it kinda was an underdog to begin with. A Conroe core Intel E2180. 1.86GHz of dual core fury. Which I managed to get to 2.7GHz on some weird ASRock hybrid DDR/DDR2 and AGP/PCIE mix board with the stock cooler. I had no idea what I was doing. I was on the stock cooler. I just pushed bclk. I had no idea back then that the DRAM and FSB were all linked back in those days. So when I reached that 2.7GHz was it because the CPU was falling on its face. Or just my off brand DDR2 667 Sticks had reached their limit. I guess I will never know. But I do have an E2200 that I have knocking around in the garage somewhere that I really want to test out and see what I can do with it. But I don't have a good motherboard for it.
Then finally my last two favourite processors both tied for third I guess. My Athlon2 640 quad core. My first ever quad core. Got it to 3.9GHz. That was fun. And my Phenom 2 965C3. 4.2GHz. 4 blazing fast cores that were arguably the exact same cores in my athlon. But that L3 made a difference to the performance.
My most hated CPU of all time. I had an Intel Wolfdale E7500. I dont know if I got a lemon. Or if my board was rubbish or what. But after reading reviews and seeing people pushing through 4GHz on Wolfdale I couldn't wait to try my hands at it. Best I managed was 3.6 and I really felt let down. Suffice to say it didn't last long.