I'm going to break this out into parts:
1 - "He's not dead; he's only sleeping" or, "It's only a flesh wound". Cast immediately or almost immediately after death in combat. Fairly common.
2 - "Come back here." Cast immediately after a death effect spell. I find it simply wrong that Raise Dead cannot counter Slay Living. If cast immediately, Raise Dead counters death effects that leave the body intact; Resurrection counters those that don't. Essentially they're counter-spells, so there's no level loss.
3 - "Perhaps his spirit still lingers". Raising a little after the event. Say the PCs want to raise a PC after the combat. They rest, memorise the spell, etc. No problem with that. Spell behaves as normal.
4 - Wish. See 2
5 - "Please raise our fallen friend". This is a good excuse to further the plot, shift them onto a side-trek, remove excess wealth / magic / whatever or any combination thereof. I'm of the opinion that a good GM should think about this sort of situation and its ramifications before it arises. Do you want to allow this? If PCs can be raised, what about others in the general populace. How does this affect assassins etc?
Also, in instances 1 and 2, I allow Raise Dead et al to be cast as a Standard Action, as long as they're cast from a spellcasting slot, not a scroll.
I could add more, but the C&C3Demo has just finished downloading.