Way back in the day, I used a Cyclo Rivoli. These were the "el-cheapos" that bike shops sold in quantity for under 5$ each. They would sometimes break but it was usually operator error.

I still use a Cyclo just to free up tight links. But I also have the Park CT-1 (or CT-2) one of these, its the early version of their professional chain tool and its very powerful. I doesn't have that second setting for tight links like the newer version does. These have replaceable pins. I think that the more powerful tool deserves some respect because, even if misaligned, it will try to power through the rivet thus damaging the (replaceable) pin. If you get the Park CT-3, be sure to get several extra drive pins at the same time.

I also bought the Park CT-5 which is Park's compact chaintool, suitable for carrying on a bike. These are well made. I think the smaller ones are nice because they have a lighter feel in the hand in this helps with aligning it better and gives more tactile feedback on just how much to turn the screw.