"A certain administration which I won't call by name took the arts out of the schools, and that left the brothers out on the street with nothing, so they went to the turntables and started rhyming. Then they had a way to express themselves, and that's the birth of hip-hop."
— Isaac Hayes
Old school hip hop comprised four ingredients — graffiti, DJ-ing, MC-ing, and beat boxing (Breakdancing is another staple, but not within the context of hip hop music, just hip hop culture). Nowadays, it is often viewed as "another name for rap".
Note that there are many different scenes, subgenres, and cultures within hip hop besides gangsta rap. Even gangsta rap has several sub-forms like Horrorcore, and Mafioso rap. Unfortunately, they rarely receive anywhere near the attention in other media (or anywhere near the record sales).
Confirmation Bias / Don't Shoot the Message: A lot of people, casual listeners and purists alike, tend to love or hate hip hop (and its subgenres) based on its messages, imagery, and other factors more so than the actual music itself.
Controversy Proof Image: Exceptions being Ice-T's cop killer controversy, which for all intents and purposes ruined his mainstream career as a rappernote Even though the Body Count album was Heavy Metal, not rap and Nelly, due to the tip drill controversy. Possibly Public Enemy as well thanks to Professor Grif's comments about Jews.
Cool Car: Exotic cars , low-riders and modded car culture in general has always been a huge part of hip-hop culture.
Stronger radio and video censorship towards Hardcore Hip Hop, Gangsta Rap, and Political Rap. MTV even refused to play a certain Public Enemy video because of a political statement. This become an extreme wall banger when you realized how the sexually explicit videos were rarely if ever banned, but violence and political statements were apparently where they drew the line.
Some even say West Coast hip-hop specifically was blacklisted because of the East Coast/West Coast rivalries, and because of this it never recovered. Then there was the death of 2pac and the collapse of Death Row Records and its rivalRuthless Records thanks to Executive Meddling (according to Bone Thugs-n-Harmony). After that West Coast rap in general, gangsta or otherwise, was persona non grata.
Conscious Hip Hop, likely due to the Afrocentric overtones not being broadlyappealing. The beginning of the end was probably when the mainstream ignored Digable Planets's more Afrocentric album Blowout Comb, and Arrested Development's follow up album Zingalamaduni.
Enemies Equals Greatness: A lot of rap songs are all over this trope, especially songs from the Glam Rap and Swag Rap sub-genres. Just about every rapper loves to talk about their "haters" in their lyrics.
Intercourse with You: This is dirty rap's very fundament, although songs about sex from artist who don't fall into that determinate subgenre are not unheard of.
It's Popular, Now It Sucks: Hip hop is often overlooked by music fans because of its immense popularity. The low quality of its mainstream artists doesn't help at all.
This largely depends on who you ask. Often if you ask somebody if they like rap music, whether they say yes or no, it's hard to tell whether they know if you are referring to mainstream "glam rap" or underground hip hop, the latter of which is generally what most music enthusiasts consider when they think of "rap".
Murder Simulators: Rap music has been a popular scapegoat for almost 20 years. The media frenzy died down around the mid 90's, then in '99, Eminem made his debut and the controversy went right back into full swing. People often blame it (and video games) for teens' insensitivity to violence and for promoting stereotypes about women.
N-Word Privileges: Black rappers use the word "nigga" constantly, White and Asian rappers do not. Hispanic rappers, oddly enough, do use the word however.
Though some white rappers either challenged this concept, or were caught using it in the past much to their embarrassment. White rapper Lil Wyte has used it numerous times in his songs and White/Asian rapper V-Nasty mistakenly thought she had these privileges in her earlier songs and faced a huge backlash over it, much to her embarrassment (though she still continues to use it to this day). While Iggy Azalea hasn't used the word herself in any of her songs, she's used the word in public saying that "it's OK because black people do it". In general though, most non-black (or hispanic) rappers won't touch this word with a ten-foot pole.
Token Minority: Female and/or non-black rappers, at least in North America. In countries where Africans are non-existent or a tiny minority, the majority of rappers will be whatever is most prevalent.
Interestingly enough for most of The Nineties female emcees was quite common. So much so that arguably they wouldn't count as a Token Minority. But after the turn of the millennium all that changed. This has been brought up in a lot of Hip Hop mags and blogs.
Female rap does seem to be entering something of a renaissance as of the early 2010s, though.
In Australia, talents like Diafrix, 1/6 and N'fa (who worked with Heath Ledger, believe it or not) head the very small number of African-Australian emcees. Indigenous hip-hop is another significant minority subculture.