I've got the top of an old rusty bolt sticking out the ground in a corner (see image) I've tried flattening it with a heavy hammer. Can't get a hacksaw in there. Suggestions for leveling that bolt to the surface?
Since it appears to be in dirt, dig it out would appear to be an option. If there's actually concrete under the dirt, chisel it out is still an option.
I'm unclear as to how that's not accessible to a hacksaw - looks plenty accessible to me. Other than a hacksaw, a sawzall (reciprocating saw) or angle grinder with cutoff disk are typical powertool approaches. An oxy-acetylene cutting torch would be another way.
Since you were able to flatten it with a hammer, it may be soft enough that a single-jack and a cold chisel might do the trick. There are also some small hacksaws where the blade extends by itself without the surrounding bow, but they are usally fairly awkward to use.
You could always drill it out with a HSS drill bit.
(Probably cheaper than buying a new tool if you don't already have one; but if you do have one, Daniel's answer is better.)
Whether it is rebar, nails, or any kind of metal I use an angle grinder with your discount blades (the $5 10-pack from HF).
You can level something like that in 15-20 seconds and dirt doesn't matter (I might choose my $20 angle grinder if dirt was in the way).
Wear glasses if you value your eyes but it is a quick job. Also more expensive blades are useless. If I use a cheap blade I can go through 5-6 rebar rods. If I use a great blade that is 10 times the price I can go through 7-8.
An angle grinder is probably going to get the job done (Yes, Daniel, it's been mentioned!) but if it couldn't simply grind off parallel with the surroundings, due to lack of space (which doesn't look like a problem), a slightly longer job is to grind it parallel to the rod 9downwards), working across it.