The great thing about this is everyone has different needs.
Welded on metal pegs/ so they wouldn't break off anymore
Added an extra radiator/ so when I mashed my fan from crashing, I still could finish the race.
Air in forks/, great way to be able to jump mx doubles without bottoming!
Chain guide(real one)/ anyone serious about offroading has this. Why doesn't bmw/ktm/suz/or kawa have them?
fork brace/anyone who rides agressive has one
rim locks/if you are in the rough, they are lifesavors, if you go where I go you have to have them
K&N air filter/ great for water, lasts forever. have ridden about 10,000 miles including an national enduro, on the same filter service!!! Also have 82,000 miles on same filter! and bike!