A Bitcoin vanity address generator will help you generate a custom Bitcoin address. A vanity address is like a vanity license plate for cryptocurrency. Examples of vanity addresses:
Of course these are not real addresses but an example of vanity addresses. Are they a necessary thing? No, but they are fun. Are they safe? Absolutely not safe unless using split key generation. I do not recommend generating your own Bitcoin vanity addresses unless you have well researched doing so and understand the risks. There are quite a few examples of Bitcoin stolen from vanity addresses. If you must generate a Bitcoin vanity address the best way to do so is to through the VanityGen application itself. Using the application run on your own computer ensures you are the only one with access to the private keys.
A lot of web based vanity address generators exist. These generators will often do short vanity addresses for free but require payment for the longer ones. Since generating a 5-character or longer vanity address requires a lot of computing power these sites often charge per character for keywords of a certain length.
BitcoinVanityGen.com – Up to six letters for free. Payment in Bitcoin for longer addresses. Safety unknown to author.
VanityGen Wiki – Read more here on Bitcoin vanity addresses.