Yasir Arafat hit the final two balls for four as Sussex stunned South Group rivals Surrey on the first night of the new NatWest T20 Blast season.
The Sharks looked to be struggling at Hove when trying to overhaul their opponents' total of 171-7, they were left requiring 15 off the last four deliveries.
However Ben Brown blasted Jade Dernbach for six and then Arafat was the hero at the death, sending the England paceman to the fence twice to seal a two-wicket success over last year's beaten finalists.
Jason Roy (57) and Gary Wilson (50) had both hit half-centuries for Surrey while all-rounder Luke Wright made 56 in Sussex's reply.
Hampshire were highly fancied before a ball was bowled in the tournament this year but they suffered a surprising 10-run defeat to Glamorgan at the Ageas Bowl.
The visitors posted 161-7 with several batsmen getting starts, Jacques Rudolph top-scoring with 34 while skipper Mark Wallace contributed 33.
Danny Briggs picked up 3-26 to restrict the Welsh county, though Will Owen claimed a trio of wickets himself to make sure Hampshire fell short in their reply.
Their cause wasn't helped by the early loss of Michael Carberry, called up to the England limited-overs squads earlier in the week, or Liam Dawson having to retire hurt on 10 due to a leg injury.
At Bristol, Craig Kieswetter continued from where he left off last season in the shortest format of the game, making 55 in Somerset's 18-run triumph over neighbours Gloucestershire at Bristol.
Wicketkeeper-batsman Kieswetter, who scored 517 runs at an average of 65 in 2013 in the domestic twenty20 trophy, helped the away side recover after losing skipper Marcus Trescothick to the first ball of the match.
Alviro Petersen (51) also made a half-century but Somerset didn't find it easy going against a Gloucestershire attack that was led by James Fuller (4-32).
Yet the team from Taunton had a trump card of their own with the ball, Australian Dirk Nannes marking his debut for the county by taking 4-21.
Max Waller also picked up three wickets as the home side were bowled out for 138 in 18.4 overs. Their only batsman to prosper was Hamish Marshall, the former New Zealand international hitting seven fours in his knock of 54.