[onion2k]

I really like "3 point estimates". Rather than a single estimate you give three - one that's your expected timing, one for the best case if everything goes perfectly, and one absolutely worst case scenario time. The difference between "best case and expected", and "worst case and expected", indicate the risk factor. If best case and expected are similar then it's a low risk feature - you understand the complexity and there are few unknowns. If the worst case and expected are similar then it's a high risk feature that you don't expect to go to plan.

I've never been in a position to actually use this approach well, but I like the idea of it a lot.