By chance, irb and ruby-console tab completion discovery. Made my day!
irb(main)> t = => ... irb(main)> t.m #[tab] t.mday t.method t.methods t.min t.mon t.month

Rails Console
>> #[tab] Feed.find Feed.find_all Feed.find_all_with_deprecation Feed.find_all_without_deprecation ...

Win XP, ruby 1.8.5 and rails 1.2.2. Google away if not on your machine.

irb is incredibly underappreciated, it has a bunch of nice things that people don’t know, like sub-irbs, lots of configuration, syntax-highlightin extensions.. :)