Ultimate Magus- best spells for Expanded Spell Knowledge

[Werephilosopher]

What are some good options for the UM's Expanded Spell Knowledge?

[Zanos]

Anything you're not sure how often you'll need in a given day. Fly, Dispel Magic, Teleport, Knock.

[Droningbass]

I think that this decision really depends on your character role is, and the type you are running.

My basic advice would be: focus expanded spell knowledge on the Wizard Spells that you always find yourself casting or needing. This way you will almost always have these spells available.
A secondary consideration is to consider focusing expanded spell knowledge on spells that do not allow for a saving throw, since your spontaneous casting class will likely have lower saves. If you have any Spell Focus feats, that can alleviate that concern to an extent.
A last consideration would be to be sure that you are able to fuel any Reserve feats you might have, such as Minor Shapeshift and the like. Knowing the required spells ensures that you power those feats until you've cast every last slot of that level.

I can suggest a few spells to consider, but the ultimate choice depends on your character and his/her role:
Level 1: Lesser Orb of (Insert Preferred Energy Type here), Magic Missile, Mage Armor, Charm Person
Level 2: Scorching Ray, Invisibility, See Invisibility, Knock (although stocking up on scrolls/a wand of See Invisibility and Knock is probably the better idea)
Level 3: Fly, Fireball, Dispel Magic
Level 4: Orb of (Insert Preferred Energy Type here), Greater Invisibility, Dimension Door, Charm Monster
Level 5: Cone of Cold, Dominate Person, Teleport

Hope this helps! Have fun with the Ultimate Magus!

[golem1972]

Nerveskitter is the first one I pick up.

[Biffoniacus_Furiou]

You can get Versatile Spellcaster in RotD and spend two spontaneous spell slots of the same level to cast any spell you know of one level higher, regardless of which spell list it's on. So Expanded Spell Knowledge isn't all that useful or important, as whatever spell you pick will already be a spell you know and have in your spellbook and could already cast using your spontaneous spell slots.