Semi-auto pistols for one-handed operation...
In my opinion, I would look into a 9x19mm(9mm Luger) with full ambi-controls that you could quickly operate under stress or with gloves.
Some brands to look at(depending on your budget or tastes):
The Walther PPX or PPQ M2; the new PPX has large easy to see 3 dot sights, it's hammer fired & DA only(no cocking or hammer spurs), full ambi controls. The PPQ costs more but it's got a good backing from many Walther owners all over.
The HK P2000 or P2000sk LEM(law enforcement modification); it's a robust, well engineered pistol that you can buy in 9mm or .40. The controls are on both sides & the LEM format is DA only.
The PX4 C(constant) or the PX4 Compact(with full ambi controls). I owned a PX4 C 9mm in 2009. It was great. The semi auto offers low recoil, easy to clean/field strip, has 17rd magazines(in the 9x19mm caliber), and it has only the slide release & magazine release(that can be switched).
The P250 line from SIG Sauer; the DA only pistol, like the Beretta PX4 C model, is easy to carry, easy to strip/clean, comes in multiple calibers(9mm, .40, .45acp). The P250 can be quickly converted to a full size, compact or sub-compact. You just switch the fire control system, barrels & pistol magazines.
NOTE; in 2013, the SIG P250 polymer frames might be hard to buy or obtain due to the huge demand for magazines/parts/weapons.
In general, Id look at the 9x19mm caliber over the more powerful .357sig, .40S&W, 10mm, or .45acp. You can pack more rounds(15/17/20/30 etc) & be more prepared to fend off a attack. The 9mm, to most shooters has low recoil so it's better to shoot one handed.
A green or red laser aimer/laser-grip might be worth adding too.
Clyde
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