These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Awesome Music: Unorthodox Jukebox has many enjoyable tunes, but "Locked Out of Heaven" and "Treasure" will most certainly start any party. "Gorilla" also counts, if for it being over-the-top and hilariously So Bad, It's Good.
Doo-Wops & Hooligans may be largely comprised of teenybopper high school dance songs, but in hindsight "Runaway Baby" from that album gave us a clue that Bruno was capable of more than teenybopper crap.
"Uptown Funk", full stop.
Dude, Not Funny!: "Grenade" has some descriptions that obviously are meant to be used to show his feelings, but instead come across as plain not funny or fitting, this includes all the suicide references.
Ear Worm: Today, I don't feel like doing anything... (whistles)
Up. Town. Funk you up. Uptown Funk you up.
'Cause you make me feel like/I've been locked out of heaven/For too lon-on-ong
Fridge Logic: In "Grenade", the singer calls his lover out because her eyes were open when they had their first kiss... which he couldn't have known unless his eyes were also open.
Despite "Marry You"'s failure in the U.S., it was a massive hit in New Zealand.
Growing the Beard: Unorthodox Jukebox in general has been better received than Doo-Wops was, thanks to toning down the Wangst with breakup songs (compare "When I Was Your Man" to "Grenade") and toning down the silliness of Silly Love Songs. The fact that it contains some excellent throwbacks to the 70's and 80's doesn't hurt either.
Just Here for Godzilla: Many of his features. For example, "Uptown Funk" wouldn't have been nearly as big a hit for Mark Ronson if he wasn't involved (in the U.S, it probably wouldn't have become a hit at all!)
Memetic Mutation: Cuz my heart breaks a little when I heeeaaar your name...it all just sounds like (insert funny sample of your choice).
Poor Man's Substitute: Many consider him to be this for the late Michael Jackson due to similarities in vocals and musical style. This is justified as Bruno was a Michael Jackson impersonator when he was very young, and MJ remains his greatest idol to this day.
Wangst: "Grenade". The narrator loves the girl to the point that he would kill himself in spectacular ways, but the girl won't do the same.
"It Will Rain", another breakup song about a girl leaving the protagonist sung with very over-the-top histrionics. The two songs eventually gave him a reputation for being an overly angsty teenybopper until his next album Unorthodox Jukebox saved him from this reputation.
This trope is why some people dislike his music; a good portion of it is about his feelings and breakups. While some artists do this, Bruno Mars goes so over the top with it, it's hard not to be bothered.