Here are some of my ideas:
Batrider
Flaming Lasso cast range increased from 100 to 1000. Is not instant, has a brief animation and travel time to it but is otherwise just as reliable as default Lasso.
Reasons
Balance: For 4200 gold Batrider gains a ranged option at enemies rather than having to jump in and risk himself. Both blink dagger and force staff together cost 4500 gold, and offer up to 1200 range of initiation, with Batrider force staffing himself half the distance back into his team. With the aghanim's upgrade you could do it differently and cast from 1000 range away. 1000 range is the distance of a lvl 1 pudge hook. It's reliable though, so not a skill shot like hook. Remember though this is an ultimate and a 4200 gold upgrade, it's not like this is game breaking. Also, the lasso stays the length at which you threw it, so you must still drag the enemy into your team. If that is too weak then you could make Batrider tug the rope back a bit (500 distance) so the unit is dragged a distance behind him closer than 1000.
Thematic: Fits Batrider's wrangler theme, makes the lasso fun to use, feels like the "ultimate" lasso.
Anti-Mage
Blink now costs 0 mana. For each point Anti-Mage has in agility, Mana Void deals +1 additional damage.
Reasons
Balance: This removes Anti-Mage's reliance on mana, leaving his mana pool and int stat there for game mechanic reasons. His mana void damage isn't as bad in most situations, since you can deal significant damage if you have enough agi built. This encourages an Ethereal Blade + Mana Void combo, but eblade is not necessary. Mana void still has a mana cost, but he gains the benefit of a manaless blink, which allows him to always escape reliably. Overall it makes Anti-Mage a more versatile hero who doesn't have to rely on mana, neither his own or his enemies, to do the job.
It would be really cool to remove his mana completely, but I think the ramifications behind that choice would affect balance negatively. (It would essentially make his int stat worthless and his mana would be used for nothing at all.) I did have a more radical idea in mind, but there is nothing else like it in Dota so I didn't feel like sharing. It basically involved replacing his int stat with an entirely different stat that offered different benefits than int.
Thematic: As I said earlier, it removes Anti-Mage's reliance on mana. Anti-Mage dislikes magic, so he shouldn't have to bank on it to save him or deal damage to enemies. Agility is his primary stat, so using that as a damage bonus to Mana Void is like Anti-Mage using his own monk-like skill to defeat his enemies. It is like Anti-Mage has achieved a kind of "ultimate" feel in regards to his spell casting and gameplay.