I suggest that you don't write the lexer by hand - use flex or similar. The task of recognising tokens is not that hard to do by hand, but I don't think you'd gain much.
As others have said, recursive descent parsers are easiest to write by hand. Otherwise you have to maintain the table of state transitions for each token, which isn't really human-readable.
I'm pretty sure ANTLR implements a recursive descent parser anyway: there's a mention of it in an interview about ANTLR 3.0.
I've also found a series of blog posts about writing a parser in C#. It seems quite gentle.
