Hilltop Hoods - "The Hard Road"
Hottest 100 Ranking - 3 (2006)
Pioneers within the scene, their The Calling album was the first Australian hip hop album to go platinum, while The Hard Road was the first to debut at number 1. "The Nosebleed Section" is generally the song of theirs highlighted as a touchstone (being the highest place Australian song, and highest place song of the 21st century in Triple J's 2009 Hottest 100 of all time list), but "The Hard Road" is the song that I'd single out.
Butterfingers - "Yo Mama"
Hottest 100 Ranking - 17 (2004)
Probably more alternative in styling than hip hop (though generally regarded as a hip hop group). Whatever you think of the lyrics, the first time I heard this it put a smirk on my face. Add Butterfingers to the list of groups to have emerged from Brisbane as well.
Illy - "AusMusic Month medley"
Hottest 100 Ranking - 66 (2013)
Illy's reworking of Australian classics from Paul Kelly, Silverchair, Hilltop Hoods and Flume is a joy to behold, and a perfect showcase for how sampling (more lyrically and through melody in this case, rather than direct from the original song) can be used to create something new and unique. Unlike some songs that have had recent chart success.
Seth Sentry - "Dear Science"
Hottest 100 Ranking - 26 (2012)
With 2015 nigh upon us, Seth Sentry speaks for us all in the disappointment of a lack of hoverboards.
The Herd - "77%"
Hottest 100 Ranking - 46 (2003)
Controversial. Politically charged. Angry. Powerful.
Without commenting on/endorsing/dismissing the merits of the concerns, social and political commentary (or the extremely explicit language (apparently more complaints were received by Triple J over the language used compared to the sentiments conveyed), this serves as a great example of protest through song, and 11 years on, you can still feel their passion.