The BugHunters RPG (powered with TSR's Amazing Engine system) provided a quite simple character sheet, and quite a detailed skill tree. For the needs of my own 6-year long campaign, I had to insert the BugHunters skill tree into a character sheet. I also seized this opportunity to add a goodly number of skills, enhancements, and specializations, as well as a few useful details (stamina and body penalties, automatic dodge chance, etc.).
Inspired by Starship Troopers, I also added psychic skills on the bottom left of the sheet. However, in order to play "vanilla" BugHunters, this part can be safely ignored.