3. Oak - Here I'm writing about regular red oak. The rift sawn oak does not have the same effect. Every time I work with oak I have irritated hands. A lot of small splinters, not too painful but plentiful. The body accepts them fairly well and basically shrugs and say "eh... they will go away in there own time". Meanwhile you fuss with them for the next 5 days.
2. Vertical Grain Fir - This wood's soft and pronounced straight grain really packs a punch. Catch an edge and it will lance you with a gigantic splinter. I have had 8" splinters. Much like you were shot with an arrow. Very painful, but it doesn't last long as it is fairly easy to grab hold of such a large splinter and remove it. No tweezers needed, maybe just a band-aid.
1. Wenge - Worst by far. An exotic wood (Africa) that will give you splinters just looking at it; small dark splinters that will keep you uncomfortable for a couple days. It's very difficult to tweezer all of them. This wood species gives six splinters at a time instead of the traditional one. The bad thing (or good) is that the body will reject these intruders fairly quickly and work it out faster than most other woods (opposed to oak). I surmise this is owing to the exotic properties and natural oils in the wood. Keep gloves close by when using Wenge.