i've got a charter undercover and love it, and they can be had fairly inexpensive new or used. and the new ones, from all accounts, are as good as the originals.
the keltec p11 and similiar series is a good choice. i want to add one to the collection, just gotta have time, lol.
any older, ie: pre-lock, s&w you can find. pinned and recessed? even better! but they will start to climb the price scale. though i'll add every one i can afford.
ruger sp101 is a good choice, though they are a bit heavy. could be because they are built like mini tanks. i love my 3" in 327, just wish they made it in a shorter barrel length.