Spoke wrenchs are probably one of the least expensive tools out there. Park tools are generally fine. I have a Pedro 3 size in one wrench so I don't need to buy multiple wrenches for different nipple sizes and the shape of the tools is comfy if I'm dealing with a lot of work or really tight nipples. It aslo has deep sockets so the nipple fits nicely into it.

http://www.rscycle.com/s.nl/it.A/id.13534/.f

I have a park lock ring wrench and I just put a penny under it to make it fit better to the lock ring. Pliers are superior but I don't use it often enough to warrant buying a pair.