My favorite killstreak so far is the pack of dogs. That is fucking awesome and hilarious.
Killing someone with the crossbow is insanely fun and satisfying as well.
I've been playing combat ops until they get all the stutter/lag bugs fixed. The recruit level bots are pretty fucking stupid and will run right past you or take forever to aim or take like 1 shot at a time, even with a full auto rifle.
sometimes they are pretty good though. I usually die to a bot sniper.
Normal is the next highest and there is a huge difference in AI. They are much better and like to use the different grenades a lot.
Haven't tried anything higher. the normal bots are currently giving me a pretty good challenge.
ANother thing I notice with the bots, more so with the recruit bots, is that they seem to not go in certain areas, so you can kind of hide and snipe them pretty easily.