Please, do NOT use Entei. >.< He is...near useless.
Suicune is the only good thing from the Trio from the Second Gen. So he is fine.
Suicune@ Leftovers
Mirror Coat/Rest
Surf
Ice Beam
Calm Mind/Rest
Too bad it can't have 5 movies >.< It would be awesome if it did. I personally like Mirror Coat on Suicune, but if you have Calm Mind...it makes it useless really since you are weaking Grass and Electric Attacks that will be flying at you. Rest works good with Calm Mind, because you can get in a few Calm Minds due to Suicune's strong Defenses and when low on HP, Rest. And that allows Surf/Ice Beam to OHKO most everything if you used enough Calm Minds.
What I'm getting at is, if you want Calm Mind, don't use Mirror Coat, use Rest in it's place. And if you dont want Calm Mind, Mirror Coat can be very useful.