I use a Gillette Fusion, or Gillette Fusion Proglide. Whichever one has the extra trimming blade on the back. That really helps me out especially with the goatee. I think it has 5 blades maybe? More then the Mach 3, which I used to use, but for me it seems the 5 blades get the job done quicker with less passes.
I get probably around 4 to 6 shaves a blade, head and facial hair. Here lately it hasn't been as many since I have been waiting so long in between shaves but normally if I do it every 2 days or so I get quite a bit of use out of the blades. Personally I don't think you could go wrong between the Gillette Mach 3 and the Fusion Proglide, if you prefer cartridge style like me.
Now those can be a bit expensive, but that's all I use. They are worth it to me with the amount of use I get out of them and the way they work so well for me. I used to use some of the Schick razors though, I think those were a little less expensive but i'm not 100% sure. It seems like I was using something called the Schick Hydro 5. They were disposable though, no refills, at least on the ones I was using. Those done pretty well for me, I just personally wouldn't recommend their Gel, it seems to dry me out. But if you are looking for something that works fairly well and costs less, I might recommend those. Schick has a ton of other style razors out as well, but I haven't tried any others so I couldn't suggest those.