First up is a Garland performance of What'll I Do (1924) from one of the "Trunk Spots" of her television show, filmed in 1963. This is one of my favorites from the series for its simplicity, and its authenticity. The song was inspired Berlin's anguish at the death of his mother, with whom he was incredibly close and who's loss would also inspire All Alone (1924).
Next is a really terrific performance of You'd Be Surprised (1919), from Madeline Kahn performed live at his 100th birthday celebration back in 1988. Kahn maintains the song's intended style and perfectly illustrates how witty and risqué he could be.
For those of you who need a further fix, there is an incredibly long list of great songs and musical cast albums to plum, including songs like Cheek to Cheek, There's No Business Like Show Business, and his first gigantic hit Alexander's Ragtime Band, but these are my personal favorites, as sung by two of my personal favorites.