My favorite Magic play style can be best described as Cheerios or Eggs. Any deck that involves cycling large numbers of cards across multiple zones, moving some serious weight either by triggers or cheating on mana costs, is my forte. I play such a deck in Modern that I home-brewed and regularly secure solid records with called Colossal Eggs (making artifacts free to combo off with Metalwork Colossus), so I tried to see if I could build such a combo deck in Pioneer.
I noticed that in Pioneer, and more frequently in recent sets, that there are a lot of creatures with CMC 0 as in their mana costs are just 1 or multiple . If you wanted to, you could just cast them for 0 mana and they'll come into play with no +1/+1 counters on them and instantly die. If there are enough post-mortem triggers on the battlefield, you can chain a bunch of cards together, rip through your whole deck and drain your opponent to death. If you have multiple copies/combinations of Zulaport Cutthroat and Grim Haruspex or their functional clones on the battlefield, you can go off as early as turn 4 by casting a slough of X-costed creatures for 0 mana back to back. Draw into Rally the Ancestors, wait until your opponent is tapped out to cast it, bring back all your 0-mana creatures from the grave and they'll insta-die, surely for the win this time.
The beautiful thing is that even if you do not choose to combo out for the win, the deck still works great with a midrange or aggro play style. Since you can put however much mana you want into these creatures, you can play them perfectly on curve and beat down (preferably against a non-blue opponent) or flood the board and go wide. Hangarback Walker can flood the board even further after death to slow aggro decks down while also contributing to your win condition, Walking Ballista serves as removal, and Stonecoil Serpent just ignores multicolored creatures which Pioneer has a lot of. Thoughtseize is the best turn-1 play for any black deck regardless of archetype, no question.
Your sideboard can make the deck even more flexible, hope you enjoy! Enjoy these spicy cheerios.
