Anti-Love Song: Over two-thirds of 69 Love Songs falls into this trope, with titles like "How Fucking Romantic," "Let's Pretend We're Bunny Rabbits," "A Chicken With Its Head Cut Off," and "The Cactus Where Your Heart Should Be." And that's just the first disc!
Hell, most of Merritt's entire discography falls into this.
Also occasionally subverted into actual love songs, as with "Papa Was A Rodeo."
Their debut single, "100,000 Fireflies" is a weird kind of subversion of this trope, being at once an earnest expression of love and something much darker:
You won't be happy with me,
But give me one more chance.
You won't be happy anyway.
Ax Crazy: Merritt seems to be fond of this. Such characters appear in Yeah! Oh Yeah, Your Girlfriend's Face and California Girls (the latter with an actual ax).
Genre Roulette: 69 Love Songs contains nearly every genre of love song you can care to name.
I Am the Band: Stephin Merritt. Although there are other recurring members, such as Daniel Handler, the real life identity of Lemony Snicket. Merritt's other band, The Gothic Archies, released an album of songs about A Series Of Unfortunate Events. Drummer/vocalist/business manager Claudia Gonson is the non-Merritt musician who's had the most staying power.
The band is indeed dominated by Merritt's personality, and they've recorded barely any songs not authored by him. However, Merritt doesn't sing a word on the first two albums and only does about a third of the vocals in concert these days, the rest alternating between Claudia Gonson and Shirley Simms.
Metaphorgotten: "A Pretty Girl Is Like..." keeps getting its similes mixed up until it finally concludes that a pretty girl is like... a pretty girl.
Lyrical Dissonance: A staple of much of Merritt's songwriting. He's even said he does this on purpose so the songs can fit whatever what mood you're in, depending on whether you listen to the tune or the lyrics.
The Original Changes The Gender: Merritt frequently writes from both male, female, gay and straight perspectives, and with both male and female singers in the band happy to sing from either perspective... let's just say it never gets boring.
New Sound Album: The albums following 69 Love Songs did away with signature synthesizers and ventured into various new styles, with mixed approval.