Tofino Bay was the pick of a terrific 25-1 Navan treble for Irish champion jockey Davy Russell and owners Gigginstown House Stud.
Don Cossack and Sword Of Destiny were the other good winners for the same combination, but it was Tofino Bay's day.
The Dessie Hughes-trained 8-1 shot overcame his relative inexperience to capture the feature race, the Ladbrokes Troytown Handicap Chase - even though Russell dramatically dropped his whip along the run-in.
The nine-year-old, plagued with injury earlier in his career, was having only his third race over fences, but relished the testing conditions.
Jumping superbly, he was always travelling well, not far off the pace set by Glenquest and Zardsky.
And when he took up the running at the second-last fence it looked as though he would win comfortably.
However, Tony McCoy, who made a late switch to journey over from England to ride for his boss JP McManus, produced Like Your Style with a strong challenge.
But with Russell urging on his companion with the palm of his right hand, Tofino Bay still proved up to the task as he held the runner-up by half a length.
They pulled 11 lengths clear of Glenquest in third and Jadanli in fourth.
"I got my reins all tangled up and, unfortunately, I dropped my whip bypassing the last," said Russell.
"He really tanked right through the race and he just idled a bit in front."
Hughes said: "He'll run in a handicap over Christmas and, if the ground isn't too quick, the Irish National would be a race for him later on."
Don Cossack (30-100 favourite) got the ball rolling when landing the odds in tremendous style as he made a winning debut over jumps in the INH Stallion Owners EBF Maiden Hurdle.
Unbeaten in three bumpers last term, the Gordon Elliott-trained five-year-old shrugged aside long-time leader Sizing Gold from the second-last and won by nine and a half lengths.
Elliott said: "He will probably come back here for the Grade One Navan Novice Hurdle (16 December) which is over two and a half miles."
Noel Meade sent out 5-4 favourite Sword Of Destiny to complete the Gigginstown trio when winning a top renewal of the Irish Stallion Farms EBF Beginners Chase.
Russell's partner breezed past Darwins Fox on the run-in for a six-length success.
Cheltenham Festival winner Alderwood made a promising chasing debut for the Tom Mullins team, but slipped up on the flat close home when in third place.
Both he and jockey McCoy were reported to have escaped unscathed.
Meade said: "I think this is a hell of a horse and he was unlucky the last day at Punchestown.
"The original plan was to go for the Drinmore (Fairyhouse, 2 December) had he won the last day, but I'm not sure where he will go now."
Meade was earlier on the mark with Busty Brown (5-1) in the Grade Two Irish Form Book 'Monksfield' Novice Hurdle.
Paul Carberry brought the six-year-old through to beat Seefood by two and a half lengths.
Meade said: "I had intended to go to Cork for the three-mile hurdle (9 December) but that may come a bit soon."
Carberry sat out the rest of the afternoon as he was still suffering from a shoulder problem after his fall from the ill-fated Go Native at Punchestown a week ago.
The John Kiely-trained Joanne One (7-1) later backed up a pleasing debut at Cork to win what is likely to be an informative renewal of the Listed mares' bumper.
Drawn N Drank (12-1) stayed on dourly to claim the INH Stallion Owners EBF Maiden Hurdle, while Misca Musca (10-1) got off the mark at the fifth attempt with a solid display in the Dunderry Handicap Hurdle.