My favorite by far is my new steering wheel. It was posted in Tractionless1 thread about his interior. Just sent my shift boot, ebrake boot and ebrake handle out to Dallas Custom again. Cant wait.
I changed my interior up a little. Sadly, some of the things I did were the things you mentioned like the shift knob ect.
I did:
-Gauge on the Steering Rack.
-After market radio (wasn't my choice, but won it lol)
-10th Anni Steering Wheel
-Painted interior pieces (matte torch red)
-Torch Red Shift Knob
Although it's not anything insane, they were simple, cheap (besides the steering wheel lol) and IMO changed the interior into a completely different car. I always get compliments and I personally love how it came out.
Pics for reference:
Stock:
Current: