The Nebula Whip from Castlevania (taken in context, it's supposed to seek out evil on its own and bind it) would be fun to toy around with.
Barring that, a Green Lantern Ring would substitute nicely.
If it had to be real life...
1) Dual-sword (Darth Maul style). I can actually fight with one reasonably well. A variant where the blades split (ala Cao Pi from Dynasty Warriors 5) would be preferable.
2) Sig Sauer 226 Custom firing .40 S&W. Why? No richochet, penetrates all but the absolute best armor out there, comes subsonic, and is really fucking accurate for a handgun in its weight. Great for personal defense and sport shooting alike.
The only problem(s) is that it costs way too much for me to afford, and I would have to pay extra for importing it.