Can I "Slide" an enemy or neutral creature?

Question

So according to the wizard level 1 spell "Slide" (Spell Compendium, p. 191):

You slide the subject creature along the ground a distance of 5 feet in any direction

(Emphasis mine) and it also says Target: One creature, Saving throw: Will negates & Spell resistance: Yes. Seems clear right?

Now the flavour text confuses this situation by explicitly using the term Ally.

When you speak the word that activates the spell, the soles of your ally's feet glow yellow as he is lifted slightly off the ground. He slips five feet across the ground, into position to flank his opponent.

Question is: Can I move an enemy gnoll of the side of a bridge with this spell?

Answer 1

The Spell Compendium says rules text trumps descriptive text

The Spell Compendium on Descriptive Passages says

The first thing you’re likely to note is a descriptive passage in italics. This serves much the same purpose as the italicized descriptions of monsters in the Monster Manual: It lets you know what the spell looks like, sounds like, or feels like to cast. The text in this section presents the spell from the spellcaster’s view and describes what its typically like to cast the spell. The descriptive passages shouldn’t be considered to be binding rules. A grand gesture indicated by a spell’s descriptive passage is unnecessary if you use the Still Spell feat to cast it, and even though a descriptive passage describes you casting a spell on another creature, it might be possible to cast the spell on yourself, depending on the spell’s target entry and the rules for spellcasting in the Player’s Handbook. (3)

(Emphasis mine.) This means that it's only one possible use of the spell when the 1st-level Sor/Wiz spell slide [trans] (SpC 191-2) says in its descriptive text that

When you speak the word that activates the spell, the soles of your ally’s feet glow yellow as he is lifted slightly off the ground. He slips five feet across the ground, into position to flank his opponent.

(Italics preserved from the original.) Other uses of the slide spell besides those detailed by the descriptive text—like using the spell to throw a foe off a cliff—are totally acceptable. Note that the ally can voluntarily forgo the saving throw against the spell slide so as to be affected automatically, but a foe makes the saving throw normally. The caster will, however, have to contend with both his ally's and his foe's spell resistance if unlowered and extant.

Answer 2

Yes, you (kinda) can

For the "throwing off a cliff" part, the spell description tells you clearly that :

You cannot slide the subject up or down, but you can slide it over the edge of a cliff or other drop-off if you desire.

So you can throw your target off a cliff.

For the targeting part, I understand your concern about the flavour text, even if, to me, the text is just describing a possible use of the spell. There was a discussion about flavour text acting as rules in D&D5E but none about 3.5 I'm afraid.

I think most people will consider that this spell can target any creature, but at this point, I think it's up to your group's interpretation.

My view is that it was designed as a multi-purpose spell, useful to move friends as well as foes.