ThunderCoaster, 2005, the first hill. It was like being hauled out of the seat, then a reversed gravity denied any movements in the groundward direction before you hit the bottom of the hill. The rest of the coaster followed up with similar moments in every other direction. Oh, how I miss it...
Balder's tall hill is also quite good, but its second cousin across the border completely outclassed it before it was raped. Nowadays, Balder is the best source of air in the Nordic countries.
Piraten's hill after the S-hill was also amazing.