Rosencrantz and Guildenstern are also quasi-subverted in the trope-making story, as they are also unintentional evil minions. Hamlet has them killed anyway.
These two go on to inspire and inform several Greek Chorus duos, most obviously Vladimir and Estragon (Waiting For Godot), more recently, Jay and Silent Bob (The Askewniverse films) and even more recently and obviously, Rosenberg and Goldstein of the Harold and Kumar films.
Timon and Pumbaa of The Lion King, who then get their own Rosencrantz and Guildenstern Are Dead.
Salarino and Solanio from The Merchant of Venice are similar, only with even less relevance to the plot. They also have so little individual personality that some actors refer to them as "the Salads".
Cleomenes and Dion in The Winter's Tale.
Romeo and Juliet has Benvolio and Mercutio. Slightly off, though; both are somewhat relevant to the story.
The smugglers in the opera Carmen are often played like this.
Also Carmen's two friends, Mercedes and Frasquita.
Most productions of Macbeth often turn Ross and Lennox (or Lennox and Angus, if Ross retains his considerably large role) into this, often merging said characters with the minor lords like Caithness, Menteith, and the unnamed lord (from III.vi) in the process.
Sir Toby Belch and Sir Andrew Augueface, the two bumbling drunks from Twelfth Night, are the epitome of this trope.