ANIME-Y HIGHSCHOOL STUPID OTAKU ADVENTURE ACTION EXPLOSIONS YAY3.85 / 5.00 4,622 Views
The most mixed MMA-simulator ever!3.76 / 5.00 8,554 Views
Fighting Puzzle! Defeat the enemy using your brain!3.68 / 5.00 18,033 Views
Though if you DON'T plan on submitting it to Newgrounds, I would just suggest googling "song name a cappella". There are dozens of sites out there that have it done for you.
If you really want to do it yourself, I'd suggest watching this video and inverting it so that you have just the vocal and not the instrumental.