1 - Grab handles....I use them every single time I get in the Jeep.
2 - Rotating the rear-view mirror upside down. Again, used constantly and with my height it makes visibility much better.
3 - Upgrading my front brakes. I didn't realize how bad they were until we put an 8.8 w/disks on Erica's Jeep. The Vanco kit made a huge difference in stopping distance with larger tires.
4 - Raising the seats up 1". Coming from a 2000 TJ, the '03 seat height was noticeably lower. Lifting them back up that 1" helped both onroad and offroad for driver and passenger.
I like my LED tail lights...but mainly for the bling