One thing I really like about the Grey Knights is that the Combat Squad rule can add an extra layer of strategy to your unit equipment choices. For regular Space Marines, almost everyone has a boltgun so it's not as big a deal, but since you have so much flexibility with the GKs you can take a variety of equipment and then rearrange it into different units depending on the mission and the opponent. I have tried a few things, and I'm curious to see what clever ideas you have!

10 Terminators:
4x halberds +1 psycannon
4x falchions + 1 psycannon
2x hammers

Typical Terminator CS splits:
Standard
4x halberds + 1 hammer + 1 psy, fight high init units, ICs, MCs.
4x falchions + 1 hammer + 1 psy, fight low init hordes, heavy infantry with no spectacular CC ability.

Vs. Nids, sometimes Orks
3x halberds + 2x falchions + 0 psy, fight infantry
1x halberd + 2x falchions + 2x hammers + 2x psy, fight Monstrous Creatures

Vs. Eldar/DE
2x halberds + 2x falchions + 1 hammer + 1 psy, two identical CS since they do the charging
2x halberds + 2x falchions + 1 hammer + 1 psy


10 Interceptors
People always tell me I'm dumb for using these guys, but I almost always make their points back and more. The Incinerators and Warding Stave are just so much more valuable on jump infantry.

1x Warding Stave
2x Incincerators
2x Hammers
2x Halberds
3x Swords

Typical Interceptor CS Splits
Standard
1x Stave, 1x Incinerator, 1x hammers, 2x halberd - Fight ICs, MCs, assault units
1x Incinerator, 1x hammer, 3x swords - Fight shooty/horde squads

Vs. MEQs
1x Stave, 2x swords, 2x halberds - hunt ICs/Terminators
2x Incinerators, 2x Hammers, 1x Sword - Engage Troop squads and vehicles


And I have typically onlly done Strike Squads and Purifiers one way:

10 GK Strike
1x MC halberd Justicar
7x Swords
2x Psycannons

1x halberd, 4x swords - Advance and assault, halberd as last-ditch effort to assassinate ICs.
3x swords, 2x psycannons - Be shooty (can spread out psycannons, but usually keep them together)


10 Purifiers
6x halberds if accompanying an IC, 5x halberds and 1x Warding Stave if not
4x psycannons

5x (or 4x and Stave) halberds, with IC
4x psycannons and 1x halberd


I usually have 1-2 Stormravens to help move my units around.

So, let me know if you have other ideas for making customizable Combat Squads or if I am just doing things terribly wrong, because I am planning to add a couple more squads to my army.