According to Table 5–1: Character Wealth by Level (DMG 135) a creature possessing double typical wealth for a level 10 PC means that creature has 49,000 gp to spend and still function like a typical PC. I'm going to assume the PC wants to, like, actually also have adventures rather than devoting all his gp to exploding, despite that being a perfectly valid lifestyle choice. (Also note that, traditionally, one doesn't survive a blaze of glory, so, here, I don't either.)
Make monsters that explode
A necromancer can spend that 49,000 gp animating explosive undead creatures. A skeleton retains the original creature's elemental subtypes (in 3.5 this is air, cold, earth, fire, and water; 3e also had acid and electricity). Any creature with an elemental subtype meets the prerequisite for the feat Final Strike (Savage Species 34), which causes a creature that dies to deal 1d6 points of some kind of damage to everything within 60 ft.; other creature can make Reflex saving throws (DC = 10 + ½ the creature's Hit Dice) with success meaning half damage. With the feat Graveborn Warrior (Dragon #312 38), a creator can give an animated dead a bonus feat for which it meets the prerequisites by paying a flat extra 25 gp per creature.
(That such undead creatures count as having one additional Hit Die for control purposes is unimportant if the controller is controlling mindless undead creatures with, for example, the 2nd-level Sor/Wiz spell command undead [necro] (PH 211). Also there's the small issue of the feat Final Strike specifying that the creature must be killed (as living creatures are) instead of destroyed (as undead creatures are). I've no idea why the feat is so specific (okay, maybe this is why), but ask the DM to waive that specificity because, seriously, dude, exploding skeletons! C'mon!)
Ideally, to make the most impressive mess, you'll want a creature with the earth subtype because when such a creature is killed it creates an effect like the spell earthquake (PH 225-6). (I'm not even kidding. This is probably the lowest-level way to get an effect like the spell earthquake.)
So, in short, take the feat Graveborn Warrior, animate a few skeleton stone giants so they possess the feat Final Strike, control beyond standard capacity using the spell command undead, carefully whittle away the creatures' hp so they're easy to destroy, and store them all in an enveloping pit (Magic Item Compendium 159) (3,600 gp; 0 lbs.).
When the time is right, empty the pit, cast the 5th-level spell mass cure light wounds [conj] (PH 216) and pick appropriate explosive skeleton stone giants so as to make them all explode when a few do, and watch everyone die spectacularly: Each explosive skeleton stone giant, when it dies (again), to everything with 60 ft., deals 14d6 points of damage that's a (maybe irresistible?) "blast of rock shards" (Reflex save DC 17 for half) plus that earthquake effect.
Each such explosive skeleton stone giant costs 375 gp. Minus the pit's cost, about 120 can be created.
(Note that a lone pit should be sufficient for any number of such creatures: order all the skeletons to deal nonlethal damage then order one skeleton to grapple another then have other skeletons join the grapple. Because the creatures all enter one creature's space, they collectively form a 10-ft.-by-10-ft. Big Ball of Violence that fits neatly in the pit. They're also mindless undead creatures, so they don't breathe, don't get tired, and don't get bored—a definite plus when pointlessly grappling for hours or days in an enveloping pit. This may be for the DM—who's been a real sport so far—the last straw, though, so save some extra gp for more pits.)
This excellent answer includes two methods I also appreciate. Here's some more information on those from a different perspective.
The 3rd-level Sor/Wiz spell explosive runes [evoc] (PH 228) says that it's cast "upon a book, map, scroll, or similar object bearing written information," so it's possible that the DM may prohibit casting the spell on each page of a book to create a book of boom and rule against trying to bind into a single unit scrolls or whatever after they've been the subject of the spell explosive runes. (Maybe the DM's savvy enough to see where this is going.)
Similarly, unless the DM rules otherwise, the feat Quick Draw (PH 98) likely doesn't apply to non-weapons like books, maps, and scrolls. And keeping a batch of scrolls, each the subject to the spell explosive runes, in a conventional scroll case means at least some scrolls will be unaffected when it's time for a dispel magic to fail to affect the runes (causing them to explode) because other scrolls or the scroll case itself blocks line of effect from the dispel to the boom scrolls!
It's possible a generous DM would allow a caster simply to tie into a big pile the loose boom scrolls and retrieve the whole pile as a move action, but, unless the DM also allows doing likewise with, for example, flasks of acid, there's no guarantee. This makes the spell explosive runes perhaps an imperfect—or, if not, at least subjective—weapon not because it lacks punch but because the boom scrolls may be too difficult to disperse during battle. Talk to the DM before taking this route lest disappointment result.
But not much disappointment: Since the spell explosive runes has no particular cost but time, paper, and ink, a caster could do this anyway and hope for the best.
I endorse spending most of this gp on five necklaces of fireballs (type VII) (DMG 263) (8,700 gp; 0 lbs.). The difficulty, though, is in getting the necklaces to fail their Reflex saving throws, and that requires a high-level spell to fail against. While an attuned gem or spellworm of fireball heightened to a 9th-level spell is probably sufficient (save DC 23), if the necklaces' possessor's dying anyway (and he likely is), a spellworm of apocalypse from the sky (BV 85) (9th-level spell at caster level 20) (Dragon #343 80-1) (9,000 gp; 0 lbs.) is probably the most spectacular way to enable also dealing 290d6 points of fire damage in a 30-ft. radius spread, the apocalypse itself having dealt 10d6 points of (in this case) fire damage in 200-mi. radius, centered on the caster. (The apocalypse spell's typically overlong casting time is accelerated by the spellworm to either a standard or full-round action (the rules are unclear).)
(Note that Book of Vile Darkness FAQ explains that the artifact material component listed for the spell apocalypse from the sky instead should be a focus component, so that issue's addressed. Also note that upon the conclusion of the apocalypse spell the spellworm's host suffers the spell's corrupt cost of 3d6 points of Constitution damage and 4d6 points of Wisdom drain. I suspect this is of secondary concern.)