Okay there are a LOT I love, but here are a few:
Leave It All To Me (YES the iCarly Theme, it's my Personal Hottake that this is like a GOAT theme song..... just SOOOO good and musically complex???)
Last Kiss by Taylor, this is a song that has somehow become BURIED by sooooo many of her other songs but I remember going through one of the hardest periods of my life and hearing her sing "And I hope the sun shines and it's a beautiful day and something reminds you, you wish you had stayed" and it absolutely BREAKING ME. It's a long song that FEELS long but you WANT it to last FOREVER.
Liability by Lorde. I still distinctly remember the day this song came out and how much it struck me.
Lovely Rita by the Bugs, it's literally INFECTIOUSLY FUN!!!! Honestly George Martin is the MVP here, his piano solo MAKES the song. Also I cannot help but grin at the line "May I enquire discretely when are you free to take some tea with me?"
I'm semi-drawing a blank for an absolute fave but I'll go with Lethargy by Bastille cause it slaps <3