11 Most Influential Microprocessor

11. Intel Pentium (1993)

Breakthrough application: Brand-name processors
After a court rejected trademarking "386" in a 1991 ruling, Intel realized that it would need to move beyond mere numbers in naming its widely anticipated new processor, which had been known as the 586. So the processor giant devised a unique, easy-to-trademark identity: Pentium.
Initially critics ridiculed the name, but in fact the Pentium opened a new era in consumer-microprocessor marketing. No longer were CPUs referred to solely by numbers such as 286, 386, and 486; instead they carried a brand name that resonated in the public consciousness.
That brand gave Intel processors a certain cachet that computer owners could easily brag about. Rival manufacturers could no longer produce clones and call them "486" or the like--a chip was either a real Pentium or a knock-off. The trademarked CPU became a status symbol, and it remains so today.

10. Motorola 68000 (1980)

Breakthrough application: Apple Macintosh (1984)
When Motorola released the 68000 in 1980, it was one of the most powerful chips on the market. Initially the 68000 powered Unix workstations and servers, including the Sun-1. But the hybrid 16/32-bit processor didn't make huge waves in the personal-computer world until Apple incorporated it in 1984's Macintosh. Descendants of the 68000 powered all Macintosh computers until Apple switched to PowerPC chips in the late 1990s.
After Motorola dropped the 68000’s price the mid-1980s, the processor also saw significant use in the Atari ST and Amiga computer lines, the Sega Genesis video game console, and arcade machines. The 68K core still lives on in embedded microcontrollers used in various applications such as automotive-engine controllers, front-panel displays, and weather-monitoring instruments.

9. AIM PowerPC 601 (1992)

Breakthrough application: Apple Power Macintosh 6100 (1994)
PowerPC sprang out of an unnatural and unholy alliance among three fierce competitors: Apple, IBM, and Motorola. The tech giants threw their weight behind this new microprocessor architecture in hopes of breaking the stranglehold that Intel and Microsoft had over the personal-computer market.
Although it didn't vanquish Intel, PowerPC found a niche as the heart of the Apple Macintosh (a runner-up in our list of The 25 Greatest PCs of All Time), which used versions of the CPU from 1994 to 2006. The processor also found acceptance outside of PCs, powering several generations of game consoles, including the Nintendo Wii and the Microsoft Xbox 360. It’s also a component of the Sony PlayStation 3's Cell processor.

8. RCA COSMAC CDP 1802 (1976)

Breakthrough application: NASA Voyager 1 (1977)
The RCA 1802 was the first microprocessor in space. Due to RCA's aggressive positioning of the 1802 in the late 1970s, the chip made its way into numerous probes and satellites--most notably the Viking, Galileo, and Voyager missions. Its low power consumption and a readily available radiation-hardened version made it ideal for the harsh conditions beyond Earth's atmosphere.
Voyager 1, which carries three 1802 processors, is currently 10.2 billion miles from Earth, making it the most distant man-made object. It left our solar system long ago and is hurtling toward interstellar space, where it may someday catch the eye of an extraterrestrial civilization.
If alien engineers do find Voyager 1, they could learn everything about Earth's computer systems by reverse-engineering the 1802, which would have to make it more influential than all of the other CPUs on this list combined. What could be bigger than a processor that shapes an alien culture's view of our civilization?

7. AMD Opteron 240 (2003)

Breakthrough application: IBM server hardware
Developing computing technology is as much about change as anything else. So when it came time to move from the 32-bit world to the 64-bit world, Intel tried its hand with Itanium, a 64-bit processor that had 32-bit support. Unfortunately, the Itanium ran existing 32-bit code slowly.
Meanwhile, AMD was busy extending Intel's existing x86 instruction set to incorporate 64-bit support without any performance cost on 32-bit software. Known as "x86-64" or "AMD64," this instruction-set design premiered in the AMD Opteron 240. The design was so effective that Intel adopted it as well, incorporating the instruction set into all of the x86 processor lines except Itanium.
All desktop-PC microprocessors manufactured today use Opteron's x86-64 instruction set, and the standard will likely persist for many years to come.

6. Zilog Z80 (1976)

Breakthrough application: Radio Shack TRS-80 Model I
The 8-bit Z80 started out as an enhanced clone of the popular Intel 8080 CPU; but because the Z80 had better features for a lower price, it soon eclipsed the 8080’s popularity.
The Z80, teamed with the CP/M operating system, became the first multivendor computing standard. Much like Windows and x86 processors today, the CP/M-Z80 combo powered hundreds of business-computer models in the late 1970s and early 80s, perhaps the most popular of which was the "Trash-80."
Like many processors, the Z80 has enjoyed a rich second life as an embedded processor in consumer electronics, powering the Nintendo Game Boy, the Sega Master System, and other game consoles, as well as many Texas Instruments graphing calculators. Modern versions of the original 8-bit Z80 are still sold for embedded applications, making it one of the microprocessors with the longest continuous history of production.

5. MOS Technology 6502 (1975)

Breakthrough application: Apple II (1977)
The 6502 was inexpensive and capable: While the Intel 8080 sold for $149, the 6502 sold for only $25. Many computer hobbyists, including a young man named Steve Wozniak, noticed the inexpensive yet powerful chip and began designing computers around it. One of Wozniak's designs became the Apple II, a PC that sold millions of units and set the tone for late-1970s personal computing.
The 6502 powered many other home computers and video game consoles of the early 1980s; derivatives of the 6502 lay at the heart of both the Atari 2600 and the Nintendo Entertainment System, which makes the 6502 the most influential processor in video gaming.

4. Intel 8088 (1979)

Breakthrough application: IBM PC 5150 (1981)
The 8088 began its life as a stripped-down version of the 8086 (1978) with an 8-bit bus. It functioned well with the existing array of 8-bit supporting chips required to make a working system, so IBM chose it for its new off-the shelf computer, the PC 5150.
The IBM PC is without a doubt the most influential personal computer of all time, so it only makes sense that the system's microprocessor is almost equally influential. The 8088 has been cloned more times than you can count, and its descendants, all using supersets of the 8088's x86 architecture, power every consumer PC on the market today, even Apple Macintoshes. Need I say more?

3. Acorn Computers ARM2 (1986)

Breakthrough application: Acorn Archimedes (1987)
ARM originally stood for "Acorn RISC Machine," a name that reveals its heritage. ARM started as a simple, low-cost, 32-bit RISC (Reduced Instruction Set Computer) processor line designed by British computer maker Acorn Computers. It premiered in the form of the ARM2 in 1987's Acorn Archimedes, a 32-bit computer released only in the United Kingdom.
The Archimedes and its descendants fared well in the UK, but never reached U.S. shores. However, the ARM architecture truly shone in its second life as an embedded microcontroller for consumer electronics, powering intelligent gadgets that hundreds of millions of people use every day. ARM processors have found their way into PDAs, cell phones, the Nintendo DS, iPods and iPhones, GPS units, digital cameras, and much more. And they've done so by the billions, making ARM the most-used 32-bit embedded processor architecture of all time.

2. Intel 8080 (1974)

Breakthrough application: MITS Altair 8800 (1975)
Some people would say that the 8080 was the first "real" microprocessor, the first one well suited to general-purpose computer use. This 8-bit CPU ignited the PC revolution as a part of the MITS Altair 8800, the first mass-produced personal-computer kit. The 8080's success quickly spawned competitors such as the Motorola 6800 and enhanced clones like the Z80, expanding the microprocessor's market potential. More important, the 8080 became the foundation of Intel's 80x dynasty of successors--a long, proud line that includes the 8085, the 8086, the 8088, and chips beyond. The 8080's footprint on history is quite large indeed.

1. Intel 4004 (1971)

Breakthrough application: Busicom 141-PF Calculator (1971)
What microprocessor could be more influential than the first commercial model of all time? The 4004 was a 4-bit processor designed specifically for Busicom desktop calculators. It proved that a potentially wider market for microprocessors existed, and it led Intel--then a memory-chip manufacturer in search of a calling--to its true destiny, that of a microprocessor innovator and a trendsetter for decades to come.

(Source:http://www.pcworld.com/article/171171/influential_processors.html)