Lincoln 135-plus is what I use for 90% of the stuff I do. Compact, simple and plenty of power for most any odd-job. Will plug into a 115V 15 amp outlet so long as you run it at mid setting or lower (good for most exhaust/light fab work)
Plug it into a 20 amp outlet for thicker stuff. Couldn't recommend the unit higher overall.
I use C-25 gas for everything steel/stainless and so long as it's set up right and the welds are prepped well it has always done a great job.
I have a big old arc welder (tombstone style) for really heavy or "dirty" stuff - something a small MIG will not do well at all.