In a studio session video, Martin Garrix said he uses different versions of FL Studio he has installed, since he has not consolidated all the samples and synth sounds into one version (due to lack of time).

The official Image Line website features a Martin Garrix testimonial:

I looked for a program that is easy to use for productions and gives fast results when making tracks. I tried to switch to logic a few times but it's just not my thing. If I have an idea I want to be able to work it out really fast so I can decide if it's worth finishing. Besides that FL Studio has some really good plugins itself which I use a lot.

A few more sources:

• In this video Martin Garrix In The Studio With Future Music, at 1:40 and throughout, a very clear shot of him using FL Studio can be seen.
• He can also be seen using FL Studio throughout this Martin Garrix Masterclass at ADE Sound Lab XL 18.10.17 @ DeLaMar Theater.
• On Feb 17, 2017 Martin Garrix uploaded a "Behind The Scenes" video of his single Scared To Be Lonely which he made with Dua Lipa. He can be seen working in FL Studio, which you can get a clear shot of if you pause at 1:37.
• At 2:47 of the official video for Glitch, you can see on his laptop that Garrix is using FL Studio.

"I started with Fruity Loops back in the day, then Reason and then I learnt Pro Tools but I kinda hated it so I got Ableton Live, which is just so incredibly intuitive," says Skrillex in this interview.

Deadmau5 on FL Studio:

"First and foremost, I launch FL with the beginning of each little idea I have in my head, whether it’s a fast melody, or a drum groove to start out with. I Use FL Studio for that because I have found that the piano roll is by far the FASTEST way to “plot” my melodies and rhythms down because although I have an ear for it, I couldn’t “play” a melody to save my life. So the base of the track is composed almost entirely in FL Studio, all my piano roll / midi data is stored in FL Studio."

Avicii is clearly using FL Studio throughout this video, Avicii in the studio - The Making of Dancing In My Head.

Also in this April 2013 Tweet, when asked what age he started producing and with what software, Avicii says:

"15-16 years old, FL studio. I learned everything myself just by watching youtube tutorials and hanging on forums and stuff!"

He can also be seen working in FL Studio in this video, Avicii: Complete Compilation Of The March 2018 Sessions.

Hardwell can be seen using fl studio with afrojack

If Daft Punk used Gross Beat as per the video, then that means that they must have used some version of FL Studio.

In this photo of a collaboration between Martin Garrix and Tiesto, FL Studio is seen in the back ground on two screens. Based on the photo's recency and layout of FL Studio's playlist layout, it is most likely to be version 11.

"Some people think, "Are you crazy working with FL Studio?" But yes, I work with everything that inspires me. MY main DAW is Logic Pro and Ableton, but recently I got into FL Studio as well." at 10:45.

David Guetta can be seen working in FL Studio in this picture

According to the Image Line artists page, Afrojack has been using Fruity Loops ever since he started out producing. He says:

"I started using it when i was about 11 years old, just for fun, making remixes and mixing records through each other just for fun, FL studio felt really easy and obvious, and I never stopped using it."

Nicky Romero started producing using FL: "Before I moved in to this studio I was literally just using Fruity Loops and some speakers that weren’t even monitors, just multimedia speakers."

Porter Robinson produces using FL Studio DAW software. In an interview with Image-Line, he says he gravitated towards it after a friend recommended it, and he stuck with it because it was "more intuitive and usable than ACID," which is the software he was using prior.

He also mentions that he programs the majority of his bass sounds using Sytrus and 3xOSC. Other features he cites are useful are the new playlist, which "eliminates pattern blocks," and Edison, which he claims is critical to his workflow: "Hard cuts are crucial to the complextro style I produce, so processing audio with Edison and using its linear phase equalizer to get all my chops to roughly the same color saves me so much time."

Original source here.

Also, around 1:17:00 in this video Porter Robinson Full Twitch Livestream, he talks about being in his bedroom studio, and says:

This is where I produce. I'm in my "studio" right now, though it's not a studio because I don't use any hardware or anything. I don't know if it could strictly be called a studio because it's just me using FL in my bedroom.