At Club4AG, I normally won't list parts for my FR-S if it's just for the sake of showing you a list of modifications.
I'll do it here for the following parts for the sake of showing you something I have used over the last 2 days at two different raceways running the FR-S hard on the racetrack.RT615K 225/40-18 on all four, while not the most aggressive size choice and may not have the top time rating for track-spec radials with sub 200’s DOT tire wear rating, I have found them to be very fun and capable for Sunday racers who want to learn to drive in a arena like open track days and lessons, as well as take part in time attack to compare your skills. The choice of a few sizes and selections offered, can make your FR-S faster, or more docile, simply by being judicious on which size and profile you choose for the FR-S.The tire is very communicative in terms of giving feedback through the steering wheel and chassis. At the same time, it does communicate clearly for heat and tire pressure differences so that you can compensate via driving style or for pit stop menu of changes to be made.Even with a modest tire size on our FR-S, it is capable of sub-1:30 laptime at Streets of Willow, at 1:28 posted by me, and potentially faster for users willing to take a more aggressive run, despite the modest 225/40-18 size I choose for the sake of retaining the FR-S/BRZ's dynamic character of fun.It’s a very durable and even wearing tire from the standpoint of abuse. The tread surface and construction is also really durable and that's a plus for novices that tend to lock up the brakes, plow on the front tires, and see occasional mishaps and off-pavement excursions in the process of learning to become an ace. The RT615K withstands such situations, and after a quick brush-off of accumulated dirt in the wheels, it's ready for another fun lap session.

The FR-S we have is tuned for street with RS-R Sports-I, with mild ride qualities and capabilities with the expensive mono-tube damper design, and took to the RT615K well in terms of being able to use the tires from home, to the track quite comfortably, and back after the event. So in a nutshell, if your car isn’t a dedicated race only car, and do use it every day, the RT615K is a perfect companion tire for those occasional Sunday races, to keep on hand as an alternative to your normal street radials, to be used on the same suspension setup of mild street sports focus like the RSR Sports-i.

Winmax W2, the highest rated sport pad that is still non-metallic, have proven to be very good as normal operation city traffic brakes with low dust, no-noise pads, that work from first crank of the morning commute. The W2 has an extended performance range for the track, and while I ran consistent 1:30 lap times all day long at Streets of Willow, and at Configuration 13 at Buttonwillow, both being very demanding with RT615K mounted and hard braking on each straight ends, the W2 was surprisingly capable for the duration of two days. No fade anywhere inside of the 20 minutes per stint run groups, and very consistent and positive braking feel over the course of the runs and day lapping. I would say these are also a very nice choice for non-dedicated race cars where dust and noise can be a problem for other track-specific brake pad selection, the W2 on the FRS simply gets the job done really well.

As a side note and optional things that can be considered:

We also have Bride Seats in the car, and it does wonders for not only the safety element, but to properly fit and hold you with the right hardness of padding in a close form fitted shape so that you can feel every bit of the car's motions, keep tabs on the tire contact patch, and giving you much more information about the road and the car.  A driver harness in the form of 4 point buckled, like  Takata harness belt can also add to the holding of the driver so less driver fatigue is generated over a fun filled day at the track.
A home-brew oil cooler kit using Mocal oil plate and advanced carbon wrapped hoses and cooler core from Setrab keeps the oil temperature in check for the demands of Southern California's warmer months.
There are a few Cusco braces in strategic locations keep the frame from stressing loose over the years of track day enjoyment.  An accurate oil temperature gauge added can also help you determine if you are running the car too hard and should maybe come back and cool it down.  Engine oil temp is a nice guideline to use for monitoring the rest of the car's state of abuse, as oil temps generally indicate similar abuse and high temps at the gears, differentials, and brakes too for that matter on the FR-S, as things tend to just stay balanced over the course of the duration you are out on the track.
While many of these braces won't make drastic changes in the car's character, it does do its part in keeping the frame nice and straight after years of abusive driving.  namely however you may want to install the Power Brace - Rear Member Part Number 692 492 RM that goes across the rear cross-member bushing mounts. It can stabilize the sub-frame motions against the uni-body, under large loads created by such tires as the RT615K used today.

I almost see that the combination of Winmax W2 and RSR Sports-i as well as choice of Falken FK453 for the street and RT615K for the track, as a really well matched set of pieces for upgrading the FR-S and BRZ to something like an extension of what the designers would have included in the car, if the price constraints of the vehicles were not at the mere $25,000. As these parts only increase the joys, comfort, and capability of the FRS platform beyond that of the showroom stock, and without tainting any of the great attributes of the car, to a more capable refined state to achieve traits of the car that cost twice or more as much.

That’s the design goal I have had since day 1, of my initial delivery of the car 18 months ago, and it’s coming closer to this through each step of the testing and trial phase using parts I select within reach, and also reach of the common users who adhere to driving pleasures in a mature form. Without the extremes, without the sacrifices, and without making the specific role into a race car, but an enjoyable sports car that you can own for a long, long time.  And that is what we at Club4AG do, is not to get on the trend of buying and replacing our cars with the newest all the time, but to take a few select cars and enjoy driving, tweaking, and sharing over the course of our lives.