all noki aphone models
all samsung phone models
all sony ericsson phone models

diff manufacturer need diff tools and softwares to unlock..

some brand/model can be unlocked easily using the data cable supplied and online server based third party program. (e.g. unlock SE k750i via DavinciTeam using standard supplied cable)

some doesnt require tools at all. u just need to have the software, input the imei no, then an unlock no is provided. but this work on a limited range of phone (e.g. vodafone w900i)

however, some newer (e.g. nokia) or more complicated model (e.g. moto) require expensive or specific cable/tools and specific software to unlock it.

some software and tools can be purchased easily from ebay. but especially those cheap software, some will not 100% work on all phones of one model, quite random.