Miller Passport. It's quite literally the BEST thing ever. It's absolutly amazing for mobile work, or if you don't have much room in your garage/shop. The newer versions allow you to do aluminum mig welding. I bought mine a few years ago (older blue version) and it's made me THOUSANDS. I think it paid for itself the first 2 weeks. It stays IN my truck with a 20lb and a 5lb tank of co2, and gets used at least once a week. Most of my work now days is tig at the shop, but it's mobile also (dynasty 200dx) and I do on-site stainless repair / fab weekly, and if it's not 100% pen welds, the Passport comes out with trimix and gets me done in 1/5th the time. It's quite literally the best thing ever! My only regret is not waiting for the newer version that does aluminum, but truthfully, it's not that big of a deal for me (since I tig). If you have the cash, you simply can't go wrong with the Passport. Hands down, no contest. It's quite simply that amazing. I put a 300A Bernard centerfire gun on it with a 15' liner on it, instead of the 10' cheesy stock M10 gun. You can find those Bernard guns for ~125 nib on ebay, but their true price is closer to 400. The version I got has the indexable head, and I carry 2 or 3 different length necks for it as well. For REAL thick steel, sometimes I even run dualshield in 035 for multipass fills, usually on buckets and such. I usually stick the root and hotpass, and just dualshield it on out.
Forgot to add, best thing:
it's an inverter based welder, and will run off 110v or 220. It comes with detachable plugs at the end of the cord, for 15 or 20A 110v plugs, and a 220 plug. Takes 10 seconds to switch the plug (it screws on) to change it. I think it has one of the highest current outputs on 110V on ANY machine as well, at least it did a year or two ago. My passport was in my toolbox when I had my accident.. it was bad enough the bed warped and went into the cab a good 4", the RKI box twisted and popped open, and the Passport flew out of the toolbox, over the cab, and landed 15' away. Only thing that was damaged was the gun's LINER. I replaced the liner for 15 bucks, and ran it to this day.
My hypertherm powermax 45 did the same thing. Clear out of the truck, and landed on the cement HARD. I think it actually bounced off the curb and landed (or hit) a lightpost 20-some feet away. It didn't require repair either...