What to use for 16ft span, max 1500 lbs

You'll need to provide more information, or do more thinking, about the surroundings.

When you have a beam connecting two points, with no support in the middle, the measurement you are concerned with is "deflection." That is, how much does the beam bend or sag.

When a beam is installed in residential construction, there is concern because the beam might also be connected to drywall or plaster, and so there is a limit to the amount of permissible deflection. Typically this is a tiny fraction, like 1/240 or 1/360. (That is, one inch over 30 feet.)

If you are installing a beam that is not supporting a floor and not supporting a ceiling, but just exists to support a hoist, you don't need to worry about that. BUT you do need to worry about the other aspect of deflection: when a beam deflects, it becomes effectively shorter. If a beam is secured at the ends, the deflection of the beam translates into pulling the ends of the beam together.

If you secure your beam on a post, the deflection of the beam will pull the top of the post inwards. This could cause your entire structure (posts, beams, hoist, etc.) to collapse.

The solution to deflection is height-of-beam. The taller a beam is, the less deflection. An "I beam" is basically the perfected realization of a common wooden beam -- most beams don't carry enough load to worry about breaking the material, so much as the need to worry about deflecting the material. So the vertical part of the I is tall (to reduce deflection) but thin (because you aren't worried much about breakage). The flanges of the I are there to prevent the beam from twisting.

If you are going to build freestanding self-supporting posts that the beam will rest on with no connection, you can just use an 18 foot beam over your 16 foot span, and the deflection/shortening won't be much of a problem (as long as the beam can slide relatively freely). You'll have to worry about the beam falling over, though, so put some side supports in place.

If you don't have room for that, you'll need a beam that won't deflect very much. To get a wooden beam with (only) 1 inch of deflection across 16 feet of span with a 1500 lbs load would require 6 inches by 16 inches of cross section (4 laminated 2x16 or LVLs).

Most people are surprised by the height requirements. But there's a reason why those big warehouses have 3-foot girders across the ceiling.

This is one of those areas where steel is going to outperform wood, and where it actually matters. You may want to settle for a hoist on wheels, or an engine lift. If you insist on a beam hoist, you should absolutely talk to an engineer. It doesn't cost that much, and it is a real relief to be able to show an inspector (or your wife) a set of signed off plans.