D3
The D3...
Not much to say about it.
Warhammer 40k uses D3's every once in awhile - Rending, Manticores, & other cases such as +D3 attacks, 2 + D3 objectives, etc. Most of the time, they don't actually use a D3 - they just roll a d6, at which points two schools of thought engage in a holy war:
- Some substract 3 from any result that's 4 or higher. So, for example, a 5 becomes a 2.
- Others divide the result by two, rounding up. So, for example, a 5 becomes a 3.
The 40k rulebook explicitly proselytizes the latter, which means the former is heresy.