When do you find time to use all of those?
I realize I am weird, and I am helped more by a few brief comments from a trusted friend than by a detailed analytical string of two dozen moves. There might actually be more gold dust in the world than can be found in nuggets. But I can wrap my mind around a nugget and actually feel it, whereas all that dust overwhelms and chokes me. It seems that I simply don't know how to make use of a plethora of dust. Or a whole page of analysis!
I just installed Fritz 9 and ChessBase Light. I was just wondering what, if anything, they do different. I just did one game and it took FOREVER to do! Ok, maybe 2+ hours. 
Fritz 5.32 seems to come with everything... it's some sort of standard I guess. It's also free online for those that want it. It's outdated though and pretty weak compared to today's best engines. Best used as a casual kibitzer when playing quickly though a game to spot gross blunders. I wouldn't use it to seriously analyze something.
Fritz 6 would be a bit stronger.
I'm not as familiar with Comet B50, as I understand it it's about the same level as Fritz 5, so the same logic applies.
Crafty 19 would be significantly stronger, so best used for a more serious kibitzer, give it more time, and use for more serious analysis.
Crafty 23 would be stronger than 19.
Fritz 9 would be stronger still. Best used for more serious analysis, also be sure to give it enough time to think.
Fritz 960 is for Fischer Random chess or 960 chess where the back rank is randomized for the starting position. http://en.wikipedia.org/wiki/Chess960
Giveaway chess is also called suicide chess, where if you're able to make a capture, you must, and you win by losing all your pieces. http://en.wikipedia.org/wiki/Antichess
Mate 2.16 is just as you thought, it doesn't play a full game, but searches for mate until it finds a forced one.
Fritz 5.32 seems to come with everything... it's some sort of standard I guess. It's also free online for those that want it. It's outdated though and pretty weak compared to today's best engines.
That said, it would still happily crush all of your opponents down at your local club, and then some.
What do the differnet engines check? I have Comet B50, Crafty 19.19 and 23.01, Fritz 5.32, 6, 9, 960 and giveaway and Mate 2.16. Ok, using what brain I have, I would say Mate is to check for checkmate. But what about the others?
Also, is the higher version better than the others?