I'm assuming you're focused on melee, so even though I include spells like Arrow Mind, to use a ranged weapon in melee, I did not include purely ranged benefits, like Guided Shot and Targeting Ray. Any Ray spell is obviously worth looking at with the higher BAB of a martial arcanist. More SpC spells worth looking at (page #):
Level 0
Stick (197): Umm...it's touch ranged? There's not much for this database at level 0, and it could be useful...I wonder what effects it would have if used on your weapon and your hand, as a way to prevent disarming, since it's usually a move action that provokes to unstick things. Good "wand spell."
Level 1
Arrow Mind (15): Immediate action. Shoot your bow in melee without issue, and even be able to make AoOs with arrow shots out to your natural reach. Note: Enlarge Person already improved projectile damage, now yet another reason to buff with it!
Blood Wind (33): Swift action. You or an ally can make natural weapon attacks at range for 1 round.
Corrosive Grasp (53): Gives you one touch attack per CL, up to 10, for 1d8 acid each, so great with iterative attacks on later rounds. Can attach the damage to unarmed strikes or natural weapon attacks (against full AC) and/or to grapple damage.
Cutting Hand (57): Hand becomes bladed weapon with a +2 enhancement. Decent in a jam or at low levels.
Fist of Stone (94): +6 str and option of a natural attack is pretty amazing early game. Note, even the duration is fixed at 1 min, so other than dispel worries, a perfect "wand spell" (CL doesn't matter).
Persistent Blade (154): Sort of like a really weak Spiritual Weapon, but this spell gives flanking bonus. Best for Wiz/Rogue types, but the +2 flanking alone can be a worthwhile buff, for you as well as others.
Level 2
Balor Nimbus (24 ) / Body of the Sun (35) / Bristle (40): Grouping together since all are basically spells to increase your deadliness in a grapple. Body of the Sun damages adjacent foes, too.
Bladeweave (31) (also, has no S component): Swift Action. For duration of spell, once/round when you hit a creature in melee, it must make a will save or be dazed for 1 round.
Claws of Darkness (47): Gives two natural weapon attacks that hit touch AC and deal cold damage. They also give you a natural reach (the spell seems ot assume medium and small casters, and says a 10 ft reach, wish they had clarified for other size casters), and allow you to
slow anyone you grapple, for the duration of the grapple (fort negates). Drawback: Can't use hands for somatic components or anything else while spell is active. (In spell list, is incorrectly placed at level 3. "Text trumps table")
Combust (50): A rather crazy d8/CL damage at spel level 2, due to the "drawback" of it being a melee touch spell. Which isn't a big deal to a Martial Arcanist. Can also set the target on fire, but that's just gravy.
Daggerspell Stance (57) (Also, no S component): Swift action. Various benefits when fighting with two daggers. +2 attack/damage on full attacks; weak SR when fighting defensively; weak SR and DR 5/magic when using total defense.
Fearsome Grapple (90) (Also, no S component): Immediate action. A bonus on grapple checks. Due to gaining tentacles, if that matters to you.
Heroics (113): Gain a Fighter bonus feat you qualify for.
Sonic Weapon (195) (Also, no S component): Add 1d6 sonic to any melee or ranged weapon.
Whirling Blade (238): Turn your bladed weapon into a 60 ft line attack, before it returns to your hand. Good "wand spell."
Wracking Touch (243): Only useful to sneak attackers. Lets you deal SA damage even if the foe isn't flatfooted or flanked, and even if its vitals are out of reach. Has fort for half, should make sure DM doesn't rule that the save would apply to SA damage.
Wraithstrike: If your DM is of the 1% that hasn't banned it, enjoy your broken spell.
I'm not even dignifying this one with a description.
Level 3
Bite of the Wererat (28): Solid combat buff. Just listing this one, all of the later "Bite of the x" spells are also worthwhile.
Blade of Pain and Fear (30): Gives you a weapon attack for duration that attacks touch AC (no str bonus to damage, though) and those struck must save or become frightened for d4 rounds.
Snake's Swiftness, Mass (193): You and all nearby allies can make one melee or ranged attack. Being a standard action, the non-mass version isn't really worth it, IMO.
Spectral Weapon (197): Swift action. Shadow weapon that lets you attack touch AC. Will save allows creature to only suffer half damage from any attacks with it. Also has some utility in that you can choose any melee weapon you're proficient in to craft it as, if you run into something with high DR or such that you weren't prepared for.
Steeldance (206): Actually...not that great by RAW, even if thematically awesome ot make two swords/daggers into dancing weapons. If they could use your BAB instead of CL for their BAB (if that would be higher), might be more promising. As written, only good if you've only lost a few CL. Target says "two swords or daggers," yet every bit of text after that only references daggers, another oddity.
Weapon of Energy (236): Add energy damage (type chosen at casting) to your weapon.
