Katy Perry - 'milk milk lemonade' entirely, "coming at you like a dark horse", "sun-kissed skin will melt your popsicle", etc
Rihanna - "for you i make my bubble pop" is the first I can think actually

glad the song wasn't released... seems like it was recorded after some good drinking

also "who's that chick" final verse
Beyonce - "naughty girl" lyrics+performance always made me cackle, "signs" - whole idea like what?, "get me bodied", "freakum dress" - the concept, "party" is like so... typical
Lady Gaga - i think... "rammaramamahhgagaolala", "mamamama", "cherrycherryboomboom" are the best answers. also "g.u.y" lyrics
Demi Lovato - don't know, only heard a couple of ha songs, although, wait, "bounce like a basketball" line, "our love was made in USA" or whet
Britney Spears - "drop dead" lyrics
Taylor Swift - the whole "blank space" is cheesy, although lyrics themselves are not
that bad. I'll say it like that. nothing so special to remember or find to like about, all ha songs I've heard pretty much seem similar to me, lyrically
Ke$ha - "dirty picture"
Selena Gomez - all of her "nananananananana"-s
Mariah - reading this thread I feel like I kinda missed something about her "hip-hop"/ most of ha post 2005 r&b tracks which I don't remember lyrically at all, sorry...