Thinkpad x220 or t420s. You can get a USB3 port on the i5 t420s, but the battery life is generally shit.

x220, you need to get an i7 to get a usb3, but the battery life is great, and it's small, and you can upgrade to 16gb ram.

Stick with thinkpad. the 20 series is the last series to offer the classic keyboard. After that, e.g., x230, t430s, you get chiclet keys.

x61, x201, x220. Stick with those. I'd go with x220, but you could even get an x61, and put 8gb of ram in it...it's ddr2 though, so it will be expensive.