Craig Overton claimed three wickets and four catches to help Somerset inflict payback on Vitality Blast champions Hampshire.
Holders Hampshire were skittled for 74 at Taunton, their lowest T20 total, with Overton starring with three for eight from four exceptional overs.
It left a simple chase for Somerset and Tom Banton's breezy 40 got them home to gain revenge after defeat to Hampshire in last year's semi-final.
After Somerset captain Lewis Gregory won the toss and elected to field first, Overton and Matt Henry ripped through the visitors' top-order with the latter picking up two for 32.
Ross Whiteley (18) and Liam Dawson (15) tried to help Hampshire regroup from 27 for five but Ben Green's three wickets helped finish off their innings with 23 balls remaining.
Banton smashed five fours and two sixes during his 24-ball innings of 40 before Tom Kohler-Cadmore and Tom Abell saw Somerset home by eight wickets in the 10th over.
A fine Kent bowling display saw them ease to an emphatic seven-wicket victory over Gloucestershire at a packed Canterbury.
Chris Dent's 55 for Gloucestershire had threatened to quieten the expectant crowd but three for 13 for Michael Hogan, alongside two wickets apiece for Jack Leaning, Kane Richardson and Grant Stewart dismissed the away side for 113 after 16.3 overs.
Tom Smith got rid of Tawanda Muyeye early into the reply on his way to three for 22 but Joe Denly (35 not out) and Jordan Cox's explosive unbeaten 38 saw Kent home with six overs to spare.
Brett D'Oliveira and Usama Mir bowled Worcestershire to a 15-run success at Northamptonshire.
Adam Hose's 61 and cameos from Jack Haynes (27), Ed Pollock (23) and Mir (20) guided Worcestershire to 196 for nine from their 20 overs.
Northamptonshire reached 90 for one during the eighth over in reply before a mini-collapse and, despite 44 not out from Tom Taylor, Worcestershire captain D'Oliveira and spinner Mir snaffled three wickets each to earn them a narrow win.
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