Quoted from classicgamefan:I use a Rigol DS1054Z:
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I agree, it's probably overkill for most things pinball, but I also use the same model at work so I'm comfortable with it. Used it recently to get the sound working on my Embryon. Probably could have done it with a logic probe, but I'm more confident using a scope.
I also have a Tekronix 2000 series DSO that is older, but in some ways nicer than the Rigol.
x2 on the Rigol DS1054Z. You get 4 channels, plenty of bandwidth, etc.
My only gripe with it is the rotary encoders on the knobs are not as tight as i would prefer. But they still work just fine.
Dave at EEVBlog has lots of good things to say about them as well.
It also has lots of open source support. Do some googling on that.