Several goldbox games. Might work with death knights of krynn for example:
If you have 255 hit points and gain a level, the additional hit points will not add up because it will return to 0 and then start from 1.
If you set the character's constitution to minimum allowed (probably 3) In the character creation screen, then you can decrease his hit points below 1 which gives 0 then 255 hit points! Then you can safely increase the constitution. It is best to leave the value between 210-230 because you level up and gain hit points eventually.