OK. Someone who has been on a long time, make one post with everything that has been suggested in the past... There are a ton.
This list is no way is what is being worked on, but are suggestions that come to mind that were made over the last few years. Some are being worked on, some might get worked on, and some will definitely not be done.
18350
1 AA tube and compatibility
More throw
brighter
keychain light
headlamp
2 CR123 in 18650 tube
battery fuel gauge
better clip
tritium slots anywhere they can be put
stainless steel tail
metal switch
Strike bezel
smooth bezel
titanium bezel
remote tail switch
more lumens
more lumens
charging port/programming port
more lumens
these are just some that I remember off the top of my head.