ESB - Extra Special Bitter

ESB - Not all that Bitter Actually.

ESB - Extra Special Bitter (or Extra Strong Bitter, whichever you prefer) is the traditional Pale Ale style from which the American Pale Ale style is derived. The style first started in England as an extra-strong version of the 'best bitter' style and simply denoted a brew with more alcohol (not necessarily higher quality, mind you.)
Today, the only true ESB in the UK is the Fullers ESB brand. In the USA, however, we have reinterpreted the ESB style to one of a moderately hopped, medium-high malty, reddish, non-citrus hopped, pale ale.
A hallmark of this style is its drinkability. ESB is a style that is balanced between malt and hops with a slight advantage being given to the hops. Malty sweetness is quietly present but is a partner to a refreshing, pleasant finish that may include a little fruity esthers.

The Beer

A base of 2 Row (sure, English 2 Row might be 'to style' but whatever) is accentuated by your standard Pale Ale cronies of Crystal and CaraPils. From there, toasted malts in small amounts, or Munich, or Vienna could be added for some interest and richness. English hops (Goldings, Northern Brewer, Fuggle, Challenger, Progress) are all good candidates for ESB. American versions like Willamette (a Fuggle variant) or Northern Brewer are appropriate as well.