There are lots of things that can be done "hardcore". I'm going to talk a bit about one of my personal favorites...you all know how much I love it...Ultimate Frisbee...or anything Frisbee-related.
I like to be the best. But since I can't be the best at everything, I at least want to feel like I'm doing everything in my power to be the best I can possibly be. So for Ultimate Frisbee, I sorta kinda sometimes go hardcore. Unless the ground is a little muddy and slippery and I really don't want to make an idiot of myself by falling...in which case I will tone it down a lot.
My version of hardcore is different from yours, and yours is probably different from Little Joey's over here. (Little Joey isn't real...shh, don't tell him that!)
I do a lot of prep work to make sure that I can go hardcore when I play. I love to play Frisbee, so whenever I can, I like to grab my brother and go practice. Currently I'm trying to perfect the basic things - throwing, catching, general control. Control is key in Ultimate Frisbee, something I've learned only after screwing up thousands of times cuz of a wild throw. Sometimes it'll work if you're throwing to a guy who's super-fit and about 6' 10, but normally, I don't recommend it. A crazy, random throw is definitely a last resort. (Seriously, as many games of UF as I've played, it has worked twice. The odds are not in your favor.)
And all of my practice is paying off! I can actually catch the Frisbee now...which is generally a good thing.
Anyway...when playing any sport - or doing anything, really - you have to experiment to find what works for you and then when you find what works....wait for it....DO THAT THING! Yes! Do it! Do it again and again until it's practically perfect in every way!
If you've ever played UF with me or watched me play UF, you know that my specialty is playing long. Right after the throw-off, I get my little buns over to the end zone and wait. Sometimes it works and my teammates can get the Frisbee to me, sometimes it doesn't work out that way. That's part of the game. What's important is that I'm doing what works for me, and I hope I do it fairly well. I'm always pushing to do it better, though.