Regarding the "dip in boiling water" method for first-time openings:

You paint shop has "paint can openers" that usually resemble a bottle cap opener on one end and a sort of "bent screwdriver" on the other.

The "flat" end is well suited to prying the edge of the cap "off the surface" enough to break the vacuum on some lid types, and the slight "curl" in that end works a lot better than a randomly chosen little screwdrive or the edge of a spoon (the other commonly used tools?). This doesn't necessarily make it a one-handed operation, but might be useful for someone rendering assistance.

Slightly thinning the blade end, if one has the tools to do it and if the original tool isn't needed for the paint cans, can make it a little easier to get "under the lid" on some jars.

Once the cap "pops" the lids usually come off fairly easily - the first time. For "syrupy" contents, the boiling (or warm) water may still work better for subsequent openings than working hard with mechanical aids, or may still be helpful with simple aid devices.

John