With the "Weird Science" mechanic what would be the best uses of level 1-3 spells being able to be combined into 1 item (fire a wand that has 4 spells infused into it and all fire when the item is activated)?
I like that, since a "Deathray" would be pretty cool.
Offhand, at the low levels, I'd probably do buffs or disable effects, since the uses aren't quite as many per day as you'd like and your UMD score might not be enough for the extra uses. For example, being able to buff yourself with say Bite of the Wererat, Fist of Stone, Elation, etc, would mean after the first round of combat, you could have a bite attack, a slam attack, your normal one, and +8 str/dex, and +2 con for the fight.
Typically, this is because, well, a low level damage spell, or even battlefield control spell that only lasts a little bit of time, is sort of a waste.
Later on, as you get more weird science, you can combo them together... True strike + touch attacks = single target pain. Entangle spell + Ref save based spells (fireball, lightning, etc) = Pain in an area, etc.
With pathfinder, how would you get an superior UMD check, at least for 1 encounter?
Aid another is always a good one, which hasn't been taken out. Not sure how I'd do it, but 1 rank in it as a non trained skill, as well as moderate charisma, masterwork tool and a +UMD item = good aid another check, they'd need +7 total, as a roll of 1 = fail for UMD. Maybe you could hirelings with tower shields that aid you, leadership cronies, or even animals trained to do so if your GM is lenient.
Or since weird science technically makes you a caster, obtain familiar = awesome then.
How long does the item made with Weird Magic last? In the example it says a certian item took 24 hours to make and could be used 4 times / day, implying that he made it once and could use it every day up to 4 times w/o making checks. How many items could he make? Does having the item which contains a 3rd level spell consume your 3rd level slot every day that you use the item or something?
"it requires a Use Magic Device roll at DC 15 to activate (a failed roll indicates that the device fails to activate for that user, and a roll of 1 means that the device breaks down for good). "
"If the device is used more times than allowed (by anyone), it requires a Use Magic Device skill check with a DC equal starting at 20 and rising by 1 every additional time the device is used. A failed roll means that the device breaks down and may not be used again (the artificer will have to build another). "
So 2 things, 1 roll of UMD from an ally = breaks item. Or you fail after using the unreliable option. Either or, means you need to remake it.
No idea on the weird science item limitation to be honest, it'd be handy to cherry pick a bunch of spells though and combine em for Weird science like that.