A message from TFN
This list is not in any particular order (thanks to FirstFungus for the suggestion).

1. Mind-Tricked it into blowing itself up.
   by Darth Hideous

2. Popped "The Holiday Special" into a VCR onboard and RUN!!!!!!
   by Darth Hideous

3. Install Windows ME on their main computer and wait thirty seconds for the crash.
   by computer-geekz

4. Make it fight the other 500 ultimate superweapons from the EU.
   by Rin, Destroyer of Keyboards

5. Parked it in a bad part of the galaxy.
   by Rouge25

6. Sneak Jar Jar onboard...
   by 2powerfull

7. Take the 5 inch model and stomp on it
   by Dan

8. The ol' potato-in-the-exhaust-pipe!
   by Mr. Whitmarsh

9. Throw that stupid mouse droid into the reactor core.
   by Darth Serious

10. Get a hobbit to take it to Mordor and throw it into Mount Doom
    by Grand Moff Brykoe

11. Gasoline and a match.
    by Kayn Marulil

12. Call the White House and report it as a Weapon of Mass Destruction
    by Jay Hughes

13. Control+Alt+Delete!!!
    by Alia

14. Let Jar-Jar loose in the reactor control room for five minutes.
    by Keith

15. Stick a rancor on the engines. 'nuff said.
    by Darth Pancreas

16. Chewy scares a mouse droid, which trips a stormtrooper whose gun goes off and hits a ceiling tile, which falls on the self-destruct button.
    by Rin, Destroyer of Keyboards

17. Tell George Bush it is an al-Qaida terrorism training camp
    by Walter Danek

18. Until it's proven that there exists something that this man can't infiltrate and blow up, I'm gonna have to go with Solid Snake.
    by Inebriated Wyrm

19. Have R2 set the self destruct before leaving, it's obvious that their computer security is pretty bad.
    by Admiral Helmut, Dark Lord of the Sixth

20. If there's one rule to spaceship design, it's that everything must be linked to the main reactor. I'd light a match and drop it in an air conditioning vent.
    by Inebriated Wyrm

21. Unplugged the power cord
    by Dufus

22. Got Luke to whine so much, they hit the Self-Destruct just to shut him up.
    by Ben O'Kenobi

23. Put a really big mirror in front of the superlaser.
    by Rin, Destroyer of Keyboards

24. Bribe lowly ILM techs to edit it out of the film
    by Darth Dastardly

25. I would have walked onto the green screen set and kicked it.
    by Jedi Knight Dru

26. Leave it alone, sooner or later a stormtrooper will hit the self destruct
    by Dai

27. We could shoot the Ewoks into space and let them throw rocks at it (note: this probably would work).
    by Mab

28. Drop a lit lightsaber down a central elevator shaft. Gravity pulls it to the center and all the important equipment.
    by Jedi with a normal name (Chris)

29. Build it out of LEGO and destroy it. Easy
    by BokkaDaClown

30. Inform the IRS that the Empire cheats on its taxes every year
    by NAHTMMM

31. Why does Rin, Destroyer of Keyboards always get in??? Maybe if he can destroy keyboards so well we should give him a shot against the Death Star....
    by Bin, Saver of Keyboards

32. Hired Homer Simpson as Safety Inspector for the main reactor.
    by computer-geekz

33. Take out the SIM card
    by Ed Kenobi

34. Tell Rush Limbaugh his prescription is being held at the death star.
    by Darth Linford

35. By over producing it, and causing its fan base to become alienated and dissolved
    by Snakewind

36. Taken stormtroopers to the reactor room, given them a target 10 feet away from the reactor, and told them to shoot the target.
    by computer-geekz

37. A virus! AOL!
    by Moosey Fate

38. Run Unpatched Windows XP on main computer, let hackers do the rest.
    by Bar Bar Jinks

39. Shove Jek Porkins in the exhaust port and teach him to harness his explosive flatulence
    by Kung-Fu-Yoda

40. Send RIAA after them.
    by Rin, Destroyer of Keyboards

41. Well, no superweapon can exist without a fatal flaw, so, if we were to plug up the fatal flaw of the first death star, it would cease to exist.
    by Vo`nadu

42. press the "off" button?
    by darth caption

43. Send them a bunch of spam for Twi'lik porn sites and insurance companies until the whole thing blows up.
    by Ash Kinsa

44. Just walk in and shut it down, it's not like I'm going to get hit by a stormtrooper or something
    by Jedi Master Jerry

45. * I would definitely send the Gungan special ops unit. "Weesa walkin da trench, then Jar Jar droppin da torpedoe in da hole and boom! We crashin da big ball"
    by Jabba the Butt

46. One screw at a time.
    by Vesp