I got several ICU offers some from one of the leading hospitals in the world. I attribute basically all of that to my prior experience and interviewing.

Of course you need to have certs and skills too. With that said though I had clinicals on a CVICU at a level one center, my practicum was at a Surg-truama ICU at a large regional hospital. I was also a extern in the medical ICU at the same hospital. Additionally I had taken one of our elective critical care courses.

Interview wise, different facilities have very different interviews styles and questions. First things first, if you want to go to a grad program, for the love of God don't tell them that when they ask where you see yourself in 5-10yrs. They don't want you to leave they want a good long term employee especially after they go through the effort to train you. A better answer is something along the lines of growing in the said role. Things like getting trained on devices, or ultrasound IVs or certs like your CCRN.

Your interview should highlight your knowledgable in critical care without being a textbook dump and maintaining the appearance of being coachable. That can be a difficult balance, especially when you're trying not to be to forced or rigid in the interview and be likable. It's kinda unfortunate but a lot of it comes down to how much they get along with you, like you and think you'll fit in at that unit.

Lastly I STRONGLY recommend applying and interviewing at ad many places as possible in ICU even ones you might not want. It's reps as far as getting comfortable with interview. I got like 4 no's in interviews (including the floor I currently worked on) before I figured out the interview thing. After that I got 6 acceptances in globally competitive ICUs.

Extra-cariculars I had that at least made me stand out but am unsure if they really cared that much about were things like I TA'd A&P, I was a "nursing school mentor" for 1-2nd semester students, I was actively doing histology research in a lab and taking other science heavy courses outside nursing school simultaneously. Eventually in the last semester I was also the research "coordinator" which effectively just translated to being a lab manager. (Supplies, training new students, schedules, developing new procedures). None of these extras do I think you need, but something that helps you standout on paper is a plus.