Although old, Abbot and Costello can still make anyone with a good sense of humor laugh. The show aired in the 40's to 60's, and is still one of the best variety shows ever made.
The brand of comedy is a mix between pure slap-stick and physical humor, and thought out comedy. Also, it was filmed live, so there was a lot of unintencional humor involved.
The only downside to Abbot and Costello is that it was so old, it is hard just to get a DVD or VHS that has good enough quality to hear and see what's going on.
If you love comedy, buy Aboot and Costello NOW! And if you still don't believe me that this is the best comedy you can find, listen to their most famous skit; Who's On First. It is the funniest skit I've ever heard, and it was the skit that made them famous.