any good item or spell combos you know of?

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Most interesting things you can try work rather too well in this game which makes just about anything other than hacking-away-without-thinking feel like taking advantage of the game in an unfair manner. here some things that work rather too well:

mordenkainens sword + cloudkill: kill your summoned swords for greenstones amulets

staff of the magi + cloak of non-detection: especially nice for a thief mage (backstab, invisibility, move away, hide. return until opposition is dead) but nice enough for a wizard... cast a quick spell (like spook, melfs acid arrow etc) at that nasty wizard before he knows what´s going on

simulacrum/project image + scrolls: use protection from magic as often
as you want, effectively turning a lich into a skeleton... or to use those lvl 9 scrolls over and over.

any good weapon + belm/kundane: these shine as second weapons for the dual wield style as they give you another attack with your MAIN weapon

summoning spells + haste: you don´t care if your summoned beef gets fatigued after the battle

blade barrier + sanctuary: opponents are surprisingly willing to stand around being chopped into bits

harm + ring of the ram ability (or any other damage that isn´t resisted): provided you have a decent thaco, this is one of the more reliable instant-kill combos as it doesn´t depend on things like saving throws. might need a magic resistance/lower resistance to pave the way

natures beauty + ranged attacks: blind opponents can be picked off from afar without impunity making this arguably the deadliest spell in the game

perhaps the ultimate spell combo if you got rid of the xp cap:

project image, spell trap, various single-target attack spells.

with this you can recycle all your spells by casting spell trap, then
having your image cast offensive spells at you. since project image also allows you to exceed your normal summoning limit, you can as many critters as you like, all preparatory spells AND all of your spell slots back.

oh, almost forgot my favourite: cloak of mirroring + cloak of reflection. you can bounce lightning bolts back and forth that way, anything standing in between is in for quite a bit of pain

I am quite fond of Improved Haste + Melf's Minute Meteors, or Improved Haste + Tuigan Bow, especially if Mazzy is using that bow.