trainers and sneakers (when talking about the shoes), customs (the place at the airport), news (like the ones from the tv or newspapers), socks, pants, briefs, shorts, underpants, boxers (underwear), boxershorts, drawers (underwear), underdrawers... and there are many more
• Some nouns only have a plural form, ending with s or without.
The police are looking for the robbers.
I like these pants / jeans / shorts.
Use either scissors or nail clippers.
Binoculars ar stronger than any glasses.
• Other nouns ending with s only have a plural form only with certain meanings.
customs (at the airport, not practices), guts (courage, not intestines)
quarters (lodgings, not 1/4s), clothes (garments, not fabrics)
goods (merchandise, not the opposite of bad), arms (weapons, not limb)
more information here:
by the way, the singular of means is mean