I have several style of bridgepins available. All are non-slotted and all affect a guitar's tone in subtle ways, more noticeable on some guitars than other. In general:
D-18's need black pins to match the binding and D-28's need white pins, except when they use black pins. :)
Ebony- a woodier tone, maybe a little raspy or unclear on the trebles compared to some of the others. Good for trebly D-18's as they'll calm the shrillness a bit. Ebony can have an abalone dot or be plain.
Water buffalo horn- very clear and sharp trebles, maybe too much so for bright D-18's. They can work nicely on D-28's, especially those will scalloped braces, as they'll boost the trebles a bit there. Abalone dot or plain.
Bone- very similar to water buffalo horn. Best on scalloped D-28's. They'll have either a tortoise or black dot, whichever matches the pickguard best.
Antique Acoustics- a hard plastic that gives smooth clear trebles and good bass. The black pins (no dot) are great for "vintage" replica D-18's like the D-18 GE or D-18 Authentic and the cream ones (with black dot) for D-28's.
I usually have matching end pins for all of these, if you want those. See the price list for current prices.
L to R: Bob Colosi black water buffalo pins, Colosi bone with tortoise dot, AA black, AA cream