The Portal gun (ASHPD) isn't that great in it's "gravity gun" functionality so I'd want a combination of the gravity gun (including secondary fire and extremely powerful) and the ASHPD. If that's not allowed, I'd go with just a regular ASHPD, and if I can't get that, then an energy sword from Halo, provided I could recharge it. If I couldn't, then the latest MJOLNIR armor. As an honorable mention: the Belmonts' whip from Castlevania, fully upgraded. Chain and mace and swinging from things, and just touching it causes damage, that's my kind of item.