ASIC resistance

ASIC resistance feature found algorithms that attempt to mitigate the chance of mining being exploited by dedicated hardware or chips through pipelining, known as an ASIC (application-specific integrated circuit).

History
The rise in Bitcoin's difficulty without local adjustment to the miner's hardware lead to CPUs, GPUs, FPGA (field-programmable gate array) becoming quickly becoming obsolete as each became less and less profitable. ASICs were created to fill the void once FPGAs were no longer efficient. Bitcoin's difficulty skyrocketed while power consummation grew as a consequence.

The expensive nature of ASICs limited their availability to early adopters. This lead to early criticisms of early cryptocurrencies; however, it continues to be reoccurring topic for Bitcoin, due to it's popularity and value.

Scrypt
One of the earliest attempts was Litecoin's Scrypt-based algorithm. It's algorithm is memory bound and easier to mine then Proof of Work (PoW). It was one of the earliest cryptocurrencies to be ASIC-resistant. However, an ASIC was eventually for Scrypt-based currencies on May 2014. Vertcoin is another ASIC resistant cryptocurrency using the Lyra2RE series of algorithms based on Scrypt-Adaptive-N.

CryptoNote
CryptoNote is a algorithm and application layer. Unlike Litecoin and Peercoin, it is not a fork of Bitcoin and is completely independent of all other cryptocurrencies. It utilizes a proof-of-work algorithm that's memory-bound and uses random access with latency dependence on top of relying on every new block depending on all the previous blocks, compared to Scrypt.

Proof of Stake
Proof of Stake (PoS) uses existing coins to mine new ones, known as minting. It first popularized by Peercoin. It has been criticized for the "nothing at stake" problem, giving an unfair advantage to minters with more coins, often requiring bootstrapping.

Proof of Capacity
Proof of Capacity (PoC), sometimes known as Proof of Space (PoSpace) uses space on the hard drive or static files to mine new coins. It has been noted for being a "greener" alternative due to low power consumption required by both the processor and storage device in general.

Burst was the first implement the algorithm. It was later popularized by the upcoming Chia coin.