The Tactical Squad is what makes a Space Marine army a Space Marine army. I kit mine out cheaply and to perform a specific role to keep them efficient. Special weapon (Grav, Melta or Plasma) and a matching combi-weapon in a pod, 5-10 men per unit. You then have a couple of options:
1) Stick Together. This gives you more bodies to soak up interceptor shots and a stronger presence in the enemies deployment zone.
2) Combat Squad. 1 half goes in the pod (sarge and special weapon) and the others begin on the table forming the firing line. They then walk up the board picking off one squad at a time.
Initially I was putting everyone in the pods, but the stronger starting presence seems to be a better overall option. Having someone with Tempered Helm with the firing line helps to keep things going when you inevitably start taking casualties. I don't bother with heavy weapons as either way my squads are going to be on the move so wouldn't be much help.
I was equipping them with snipers but since they consistently couldn't hit the broadside of a rhino from 3" away with a missile launcher and having stood still all game I've decided to go a slightly different route. It's simple bolter Scouts now in a Land Speeder Storm with Heavy Flamer or Assault Cannon. The Land Speeder helps protect against deep striking units such as other pods and when that's done if it's still alive the heavy flamer on such a quick platform can cause chaos in the enemy army, especially against Tau where it'll get through the best part of a Firewarrior unit at least before going down. The Scouts themselves are good at getting linebreaker but if you put them in the Speeder then they've got a nice, quick platform to fire from. Alternatively outflank them and/or the Speeder for some board edge shenanigans. Not bad at all for a 100 point unit :)