Hmm, a hard question...

Let me think, that remix of Me & U by succducc, i think i discovered it through osu!

And, looking at my faves here remembered me of some others like:

Love letter from YOASOBI

Cold as ice (PH Electro remix) [...] By Sarah Connor

And it's raining man is cool too

Exyl - Ping 2

Probably Kobaryo - Tool Assisted Speedcore and Kobaryo - Bookmaker, but osu! was really my introduction to the whole genre, so there's a lot of songs I heard from osu! first

That's a tough one, but 2 songs that do come to mind atm are:

• Anavar (Hardstyle remix) by yosuf

and

• Insight by Haywyre

Both are super fun to play

I haven't heard of Xi, Yooh or Demetori before osu! and now I can't get enough. Ice Angel is particularly a favorite of mine from Yooh, and I can get behind just about any song from Demetori -- The MadPiero Laughs, Deterministic Chaos, and Emotional Skyscraper are my favs though!

Other artists osu! put me onto has been Igorrr and Sewerslvt.