HackMaster has two types of skill checks - opposed and unopposed. Both work perfectly well, but the unopposed skill checks are ... well .. not as exciting. Also, some of them require the GM to make a roll for a player to keep them "in the dark" and I don't like that. Players like to roll dice.
So with a quick bit of mathy magic, all skill checks are now opposed rolls. The player rolls 1d100p+skill score and the GM rolls 1d100p+difficulty+50. The difficulty is based on what is already in the book. This keeps the probabilities of success the same as the original and adds a bit of mystery.
Alternate Quick Skill Check Idea
|I've also been thinking about using a simple mechanic of 2d6p+skill rank (0-5). A clever description adds +1, a really clever description adds +2. Karma, luck, honor, and the rest can add in the normal manner.|
*2d6p+skill is used when appropriate, for example when characters are having some sort of skill contest.
I haven't used this in play, but have discussed it from time to time. Not sure how it would work and I have little to no interest in figuring outthe probabilities right now.