The main goal of these random encounters is that they launch an attack, but combat does not continue for however long the dice decide to miss for! Also the monsters want to get away, rather than fight to the death! Basically it makes time matter in the dungeon, but since room encounters are (atleast in my case) the more carefully crafted ones, it makes sure that random encounters don't take too much time away from the crafted encounters.
The set up is that upon gaining line of sight, the intelligent monsters throw down oil and a torch to light it (1D6 damage to pass through) in the area in front of them, as well as setting down portable barricades of sharpened stakes, set in a spear vs charge arrangement (this isn't perfectly book legal - it essentially gives them a ranged attack AND a spear attack - it's up to you if you actually have a second squad of monsters manning the stake barricardes). They then launch ranged attacks. Typically on an NPC party the ranged attacks would probably kill one or several, so generally the monsters are horrified when it merely aggrivates the party! So the monsters run, counting on the flaming oil and barricade to to hold off the group from pursuit.
The ranged weapons vary, being mostly the cheapest kind. Generally Gnolls have darts or javalins - while the lesser intelligent monsters might only have javalins or only slings (with this influence in mind, choose as you see fit). Generally on the round after the darts or javalins are used up, the monsters will run. Otherwise they resort to using slings (but this is a rare case as these are supposed to be quick encounters).
1. Sling (1D4 damage, range: 5/10/20)
2. Javalins (1D6 damage, range, 2/4/6, ammo: 1 per ranged attack monster)
3. Darts (Three attacks per monster, 1D3 damage, range, 1.5/3/4.5, ammo: 3 per ranged attack monster)
Monsters (in numbers equal to the number of players, maximum: 5 (as this fills a ten foot corridor))
1. Giant Rats (magically controlled by some hidden monster who does not show themselves)
2. Stirges (if their attack hits, they will attach but only draw 1D4 the next round, then fly off. If they miss, they fly off)
6. Beserker (they don't bother with the oil, barricades or ranged weapons! They just run in screaming!)