Saturn:

Super Pro Action Replay 5 in 1 +

The last converter you will ever need for your Saturn. It's a 4mb RAM cart, backup cart, cheat code device, memory manager, and region bypass. You can save your games on it, use it with games that use 1 or 4mb of RAM (like some of the fighting games), apply PAR codes and play Japanese games on American Saturns. The only problem is that these bad boys tend to die early. I had one for about 3 years, then suddenly it konked out. I bought another, and it's been going strong for 2 years so far. I've read that taking the cart out of the Saturn and putting it in creates some static that kills the chips, so I'm leaving it in there all the time.

Dreamcast:

Gameshark

I had some problems with the Utopia boot disc, namely with Capcom games. Marvel vs Capcom, Mars Matrix, and Street Fighter III Third Strike wouldn't load. No problems at all with the Gameshark, however, which is a boot disc and a memory card. Besides having codes for games on it (if you like that sort of thing), it plays all imports (at least all of mine) flawlessly, and the memory card can be used to save all games just like an official DC VMU. Complaint: The memory card is ugly as sin, a black card with the gameshark logo on the top that barely fits in the second DC controller slot and won't fit in the first at all. You'll have to put it in the second slot of a second controller if you want to use your jolt pack.