Top end chargers would be Systema Fuzzy Logic or the Eagle Force Premium Charger.
TLP is a decent brand, but the fans are known to fail prematurely.
But for what you get, the TLP ones are priced quite well.
If you're charging NiCads for airsoft use, you want something that can do at least 6 cells and up to 10 cells (7.2 - 12v), a discharging feature, adjustable output, LCD display is always a nice feature, cycling functions are a nice feature, or some type of programmed discharge - fast charge function, and you want a minimum charge rate no higher than 500mA.
If it has small adjustable steps for charge rate, that's also a great benefit to allow greater control on the charge rate.