I support Tony Ennis' answer - you want the clock as your ally, not your enemy. That means you want to get your opponent out of book before he does it to you, so he burns more time on the clock. If you can play an opening he's not likely to be familiar with, but which is still playable, you're going to gain lots of time on the clock if he tries to play well.
Once he eventually decides that he doesn't have time for long thinks and just starts to improvise, you may be able to lure him into a trap or two.
Then, once you have an advantage, back off on the tactics and just grind out the win by picking up extra material or squeezing him positionally.
Expect a sacrifice/breakout if he's got a positional disadvantage, try to figure out where it's likely to happen, and have an equal or stronger threat ready, if not a refutation.
Finally, since it's a Swiss and not a Round-Robin, you will play the strongest players if you win every game. The overall winner in your section (if winning is your goal) may not need to have a perfect score at the end, so if you have a game that looks drawish, don't be afraid to offer a draw, instead of risking trying to win a drawn game. It'll probably improve your winning chances in the next few games due to the pairing rules anyway. However, you should know that if you end up on this track and at the end of the tournament, you tie on game points with another player, it's likely (if there isn't a playoff) that the tiebreak will be based on the scores of your opposition. So, if you played weaker opponents than he did, it's likely his tiebreak score will be higher due to his opponents' having fewer losses and draws than yours.
I don't go to win the section so much as to play, so for me that's not a concern.
As for openings, you might consider:
- Budapest Gambit
- Colorado Gambit
- Icelandic Gambit
- Schliemann Defense (to the Ruy Lopez)
- Bird's Defence (to the Ruy Lopez)
- 3...a6!? (to the Italian Game/Giuoco Piano)
- Pick a line you're comfortable with against the English (1...a6 and 2...b5 has been tried), and
- Pick a line you're comfortable with against the Reti (1.Nf3)
- Expect a few London/Colle/Zukertorts, which attempt to avoid an early confrontation, so have a one-size fits all system for them
- Have a line against the King's Indian Attack (1.e4, 2.d3) that you like, if you don't play 1...e5.
Also, have at least one line prepared for the Grob Attack and for the Sokolsky Opening.
- Vienna Gambit vs. 1...e5, or Göring Gambit vs 1...e5
- King's Indian Attack (KIA) vs French (1. e4 e6 2.d3 d5 3.Qe2!?)
- KIA vs Sicilian:
- e4 c5 2. Nf3 e6 3. d3 Nc6 4. g3 g6 5. Bg2 Bg7 6. O-O Nge7 7. c3 O-O 8. d4 cxd4 9. cxd4 d5 10. e5 Nf5 11. Nc3 f6 12. Re1 Kh8 13. g4 Nh4 14. Nxh4 fxe5 15. Nxg6+ hxg6 16. dxe5 Nxe5 *
- Alekhine's Defense line (I recommend 1. e4 Nf6 2. e5 Nd5 3. d4 d6 4. Nf3 Bg4 5. Be2 e6 6. O-O Be7 7. c4 Nb6 8. Nc3 O-O 9. Be3 d5 10. c5 )
- Scandinavian Defense line (take your pick)