Just wondering why bulkheads didn't make it in the top 5? First thing I broke was a set of bulkheads. RPM a-arms, RPM shock tower and body mount, and aluminum bulkheads and poof - dang near bulletproof.
I run the American CNC Machining bulkheads and love them. $62 for front and rear - doesn't take long to get to trhat replacing stock plastic ones.
I also run the American CNC Machining bulkheads and also love them! I just put all RPM arms on too. Also got a dynamite fuel filter and a motor saver air filter! You might want to add "center skid" to that list. It realy ties ur chssis together to minimize chassis flex, which leads to less chewed up spurs! And i think we all kno how much of a pain our plastic spurs can be sometimes.