Bitcoin excludes a few normal characters for the sake of readability, and a Bitcoin address can be either 33 or 34 characters long. It's:
1[1-9A-HJ-NP-Za-km-z]{32,33}
Incorrect. The smallest valid BitCoin address is
1111111111111111111114oLvT2
so the addresses can go down to 27 characters. Also, 34 character BitCoin addresses can't start with "1R" "1S" "1T" etc...
I also have the ability to generate useful novelty BitCoin addresses. The best one for me so far is
1ByteCosnsUNJun4KL3HSt1NfFdXpzoRTy (pesky s)
ByteCoin