Harbor Freight 110V one modified to use Miller tips. Works pretty good as long as I don't try to go too thick. 
Also use a spot weld adapter nozzle on my Eastwood MIG 135. Works good on thicker stuff. 

I used a spot welder from harbor freight for my last project. As I recall it was less than a couple hundred dollars. I worked OK. I just hope when I hit the first big bump the car doesn't fly apart.

The prospot is one cool tool. No pun intended. With the longer arms it has quite a reach. On the few times I have worked with this tool it's been flawless.
-Shawn

Hi , I have a Miller 220 volt which I have used for over 25 years .gone through many tips but a pretty good welder. https://www.millerwelds.com/equipment/welders/spot-welders/msw-and-lmsw-air-cooled-m11100

Also have a snap on which is basically a Lenco . https://store.snapon.com/Spot-Welders-Welder-Spot-P646241.aspx

I have recently purchased a Prospot PR 10. This is the same machine used at 7 ent by Nick Upton This is a water cooled machine. //prospot.com/products/pr-10/

Can't wait to try this one out and will probably liquidate some of my others ....

Mousy

URL: https://www.millerwelds.com/equipment/welders/spot-welders/msw-and-lmsw-air-cooled-m11100

In the market for a spot welder. What have you used, what you like dislike?. Whatever info you have is appreciated. Scott