100 - Zadra @ Energylandia
150 - Red Falcon @ Hirakata Park
200 - Kumba @ Busch Gardens Tampa
250 - Rutschebanen @ Tivoli Gardens
If you want to get into techinicalities, my 100th, 150th and 200th were actually Energus (Energylandia), Snoopys Great Race (Universal Studios Japan) and Scorpion (Busch Gardens Tampa) respectively. I went into Zadra, Red Falcon and Kumba with them being my milestones at the time, but I later found out about other creds I hadn't previously counted which threw them off but I still consider them my milestone coasters.