What coins are worth a lot?

That's an extraordinarily broad question and doesn't have a simple answer. In the US alone there have been about 20 different denominations of coins minted at 8 separate Mints over a period of 215 years so there's thousands of possible coins to look for, AND you have to decide on what the term "A LOT(*)" means!

As a brief overview, certainly any silver or gold coins will be worth much more than their face value today. As of 10/2010, 90% silver coins are worth at least 10 times their face value as scrap and gold coins are worth about 150 times face.

That said, many older (early 20th century and before) coins can be worth even more to a collector or dealer so selling them to one of those "we buy gold" places is a good way to be low-balled. Here are just a few of the hundreds and hundreds of older coins that are worth quite a bit:

Lincoln cents

1955 with a doubled image

1914-D and 1909-S VDB

Nickels

1912 Liberty head with a D or S mint mark

1937-D with a 3-legged buffalo

Dimes

1916-D Mercury head

1942 with 1941 showing underneath

Quarters

1916 Standing Liberty

1932-D

1932-S

Half dollars

1921, 1921-D

1916-S

Silver dollars

1928 no mint mark

and so on.

(*) Please be careful of this expression. A LOT is two Words. There's no such thing as "alot", just "a lot" and "allot", and they're not related at all!!