For the table, if it's there are thin pieces of metal called "mending plates" that have holes for screwing into wood. Depending on where the table is wobbling, angle braces might also be good. If the wobbly leg is screwed into the table, it might just need tightening. If it's wobbly because the floor is uneven, you can get small wedges or plastic circles to level out the high leg.

If it's a metal table, once you tighten the screws I don't have other suggestions, unless you want to use superglue to stick on angle braces or mending plates.