Well it's pretty much in my signature but here's a little more breakdown.
edit: I know you said 'just the CPU no other specs' but honestly each CPU has a story on why it was chosen. I don't just pick on one spec alone. There's a logic path for each.
4930k @ 4.3Ghz w/ a Hyper 212(fan at 100%) that keeps it in the 50-60c range under gaming loads. 60-66c under bench or render loads. This is the 4k rig but also used for more extreme FPS 1440p testing with DXR stuff. I chose this CPU due to it's 40 PCIe lanes and a great BF deal thru Newegg(around $400 for both the MOBO & CPU back then). At the time I had SLI and a PhysX setup to take advantage of the lanes. MOBO also has 3 RAID chips and at the I time was using them with six platters. Now back down to 1 GPU and not using the raids but might as SSD SATA III prices continue to drop. Just waiting to get a pair of 2TB's for a good price. More extreme enthusiasts go for the 3930k's but I've been very happy with this one and it's proven it will suffice for at least one or two more top end GPU gens. The MOBO is unusual and by no means a preferred gamer's choice but it's been great for my needs a still offers a lot of options for the future.
2600k @ 4.2Ghz using a Hyper 212 EVO that keeps it in the same temperature ranges as the one above. OC is via OC genie from the MOBO. I know I could take it higher manually but the gains are just not worth it for me. This rig is in the living room and very, very, quiet. This was my 1st post pentium 4 build. This rig is the daily use and 1440p gaming machine. Anyone who knows Intel CPU's can tell you the amazing history of this model and it's siblings. It's one for the history books with the first person, single player, games I play and it'll still hold around 50-70% usage for most and only recently started pegging 80% and higher(SOTTR). It drives that 1080TI to 80-120FPS on average in 1440p. I bought this CPU ~July/August 2011 and it's been running since except for a year or so off during the 4930k build.
5700HQ @ 2.7Ghz(boost to 3.4Ghz) in a MSI GT80 2QE Titan laptop. This was a graduation gift but an unusual beast also. 2x980m's in SLI. 2 pairs of m.2's each in RAID0 and a platter. As laptop CPU's this one has done reasonably well with the pairing of GPU's. It just fast enough to not bottleneck them much and allow upwards of 120hz at 1080p(attached monitor)for games that support SLI. Biggest complaint was the laptop display, 1080p 60hz, should've been a 100+ hz since the cpu/gpu's can easily hold 60fps for most games at ultra. Overall a fun laptop but with the death of SLI I recently re-purposed it as a music server in the cave since it's near silent, in this capacity-not gaming, and connected to a nice home theater set-up. I also just finished moving all my FLAC files to a portable HHD so I can use it a server for my DIME account which I've neglected over the last few years. I've also never been happy with the laptop's cooling solution. At max I've seen the CPU hit 80c and that's too hot for my taste. It's living a much easier life now.